Author Topic: Little Wall  (Read 2401 times)

Offline Jasonb

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Little Wall
« on: March 18, 2022, 06:57:51 PM »
This engine is based on a design by Elmer Wall that was published in "Model mechanics and Inventions" and despite asking around I have not been able to find an upto date photo of one, the best is a rather grainy image from scans of the original magazine article.



There was some talk of the old patterns having been bought, reworked and a limited run going to be produced but again I can find no sign of any of these casting sets if they were ever actually done nor mention of the original castings that Wall produced.

In redesigning the engine I opted for my usual 24mm bore which makes scaling the imperial sizes down to metric quite straight forward using the ratio of 1/16" on the original = 1mm on my drawings. At this size the original 36cc capacity comes down to 11cc. The parts were all 3D modelled in Alibre and assembled there two which allows for checking that things will fit and rotate rather than find problems during the build. This is something I have taken to doing with all models now as you can sort out legacy errors which saves headaches down the line, it is also a good way to get to think of how you are going to machine the parts.





I decided to make a start with the crankcase which was from a block of 6082. After squaring up the block and marking the crank and cylinder positions it was held in the 4-jaw to bore out to diameter for the end plates and then an HSS tool was used to enlarge the cavity to clear both the crank webs and deeper still in the middle to clear the conrod big end.



The block was then repositioned to bore the piston clearance and a larger recess to locate the cylinder liner.



For the external shaping of the crankcase I decided to make use of teh CNC, the following photos show it taking shape after each of the various stages of machining.

An adaptive clearing path was used first to remove most of the material using a 5mm 2-flute carbide cutter specifically for aluminium.



I then changed to a 6mm 2-flute ball ended carbide cutter and did a coarse "steep and shallow" path to remove most of the remaining material but leaving 0.2mm for finishing with a 1mm stepover



The same tool was then run again with a 0.3mm stepover to get a finer finish



At the time this was done I had not quite got my Z axis movement smooth so there are a few more steps than there are now but nothing a little needle file work could not sort out.

I probably showed this video in the CNC section but won't hurt to post again


Offline Johnmcc69

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Re: Little Wall
« Reply #1 on: March 18, 2022, 09:08:48 PM »
 :ThumbsUp:
 That's very nice Jason! It's nice to see some of these "obscure" kind of models being brought to light, I couldn't imagine how many there might be. I hope you have some clearer photos, or the magazine article to work from.

 I'll be following along,

 John

Offline Art K

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Re: Little Wall
« Reply #2 on: March 19, 2022, 01:59:41 AM »
Jason,
I am familiar with a lot of the Elmer Wall engines but not this one. I do recall a guy at the NAMES show who collected them this one doesn't look familiar. Looks to be a great project.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Jasonb

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Re: Little Wall
« Reply #3 on: March 19, 2022, 07:13:36 AM »
Yes I like to fine the old ones that are not about any more and enjoy the challenges of redesigning particularly the ones where I don't even have any drawings.

That is the only photo of the engine, there is another poor one of the assembled carb which was in a second article. Drawings of the engine are not too bad but the carb drawing is difficult to read.

Art, that seems to confirm what I have found or rather not found, it seems a very obscure engine unlike ones such as the Water Wizard and the other 4-stroke designs

Offline Zephyrin

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Re: Little Wall
« Reply #4 on: March 19, 2022, 09:04:57 AM »

Offline Jasonb

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Re: Little Wall
« Reply #5 on: March 19, 2022, 10:22:13 AM »
I assume so as I only have scans of the particular article. It's the CS ending not X but could still be the same mag which could have altered it's name

Offline Alyn Foundry

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Re: Little Wall
« Reply #6 on: March 19, 2022, 11:46:55 AM »
I see you’ve found a use for one of those flywheels you made the pattern for Jason….  ;)

Offline Jasonb

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Re: Little Wall
« Reply #7 on: March 19, 2022, 01:01:00 PM »
Oh no I haven't. They might just have done for the full size engine which was 4 1/2" dia  but the flywheel on this one is 74mm dia. No castings were hurt in the making of this engine ;)

Offline Jasonb

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Re: Little Wall
« Reply #8 on: March 25, 2022, 04:14:16 PM »
Once the CNC work was done on the crankcase it was then just a case of treating it like any other casting and doing the easy bit of drilling and tapping the various holes and also milling a couple of clearance notches at the sides of where the cylinder mounts to allow the transfer of the air/fuel mix.



With that part complete I turned my attention to the end covers which are almost identical, the only difference being that one has a parallel area that the ignition timing disc can rotate on and the other at the flywheel end is as "cast". The first thing to do was bore out for the bronze bearing, turn the OD and also cut a spigot to fit into the crankcase.



Having previously carved out similar details for the Stuart Lightweight on the manual machines I again took advantage of having the CNC to shape the external pockets leaving the webs that support the bearing housing. First roughing out



Then a finish cut with finer stepover



When doing the CAM I had set it to leave 0.3mm on the bolting face so the part was returned to the mill and skimmed to finished size, as this surface was going to be left as bear metal the turned surface looked a bit nicer than the CNC milled one.



While the mill was covered in aluminium chips I also made the base, this was just drilled and tapped twice from below so it could be held to a smaller block which in turn was held in the mill vice. This allowed for easy access all round the part. Not so easy to see but the outer edge has a draft angle machined into it to more closely represent a casting.






Offline Jasonb

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Re: Little Wall
« Reply #9 on: April 12, 2022, 06:40:33 PM »
The cylinder started life as a piece of 50mm dia steel bar, faced and ctr drilled for tailstock support so that the waste above the mounting flange could be removed. I did most of this with a parting tool then switched to a 1mm radius end grooving tool so that I got some fillets left in the corners as it was brought down to final size.



I then roughed out the cooling fins with the same parting tool and finished with the groover, this took a bit of setting up as due to the change in length of the fins the angle of each changed slightly as the spacing remains constant.



I used the CNC to cut the shaped holes for the inlet/exhaust boss and the simpler shaped transfer block



I also made use of it to cut the profile of the blocks on the ends of a bit of round bar, these were then cut to the undersize  inner radius of the cylinder using a boring head





A trial fit showed that the CNC had done a nice job with close fitting parts that just needed one or two strokes of a needle file and then they could be lightly tapped into place with a small nylon hammer.







Happy with the fit the parts were cleaned and fluxed before silver soldering together. After machining the inlet/exhaust boss to finished length it was back into the lathe to Finish bore the inside to accept the iron liner. Once that was done and there was no more need for a chucking piece the top of the cylinder was turned to profile and the M10 x 1 plug hole drilled and tapped. You can just see the every thin line of silver solder around the joint from the inside





The last bit of machining was t mill the slots for intake and exhaust and tap two holes M3 to hold the combined manifold in place.



Lastly I grit blasted the outside to remove any discolouration from soldering and give a good key for the stove paint I had planned for it.












Offline rklopp

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Re: Little Wall
« Reply #10 on: April 12, 2022, 07:01:48 PM »
Nice work!

Offline RReid

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Re: Little Wall
« Reply #11 on: April 12, 2022, 08:23:35 PM »
That's some fancy fin work! Sharp little beauties (literally).   :ThumbsUp:
Regards,
Ron

Offline Hugh Currin

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Re: Little Wall
« Reply #12 on: April 13, 2022, 05:05:44 AM »
Jason:

Very nice work. I'm awed by the 3D contouring one the crank case. Cylinder came out great also.

Thanks.
Hugh

Offline fumopuc

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Re: Little Wall
« Reply #13 on: April 13, 2022, 06:42:27 AM »
Hi Jason, nice progress.
CNC does allow to think about the making of parts in a complete different way.
I do like it very much.
Kind Regards
Achim

Offline Roger B

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Re: Little Wall
« Reply #14 on: April 14, 2022, 09:15:52 AM »
That's some excellent fabrication  :praise2:  :praise2:
Best regards

Roger

Offline steam guy willy

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Re: Little Wall
« Reply #15 on: April 14, 2022, 04:26:56 PM »
Is this the same  Mr wall that made the " Wall auto wheel "the attached to a bicycle  early in the 20th century ??

Nice construction  :praise2: :praise2:

Willy
« Last Edit: April 14, 2022, 04:52:04 PM by steam guy willy »

Offline Johnmcc69

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Re: Little Wall
« Reply #16 on: April 14, 2022, 04:28:59 PM »
 :ThumbsUp:
 Nice work Jason!
 That's looking real good!

 John

Offline Jasonb

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Re: Little Wall
« Reply #17 on: April 14, 2022, 06:44:39 PM »
Thanks for all the comments, will keep the posts coming now my PC has been repaired.

Willy, going by the Union Jacks in your image I don't think it is the same as my Mr wall was from the US. Some details of Elmer Wall here on the Model Engine News site. But I do like those little inside wheel engines.

http://modelenginenews.org/gallery/p18.html

Offline Johnmcc69

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Re: Little Wall
« Reply #18 on: April 16, 2022, 01:39:54 AM »
Hi Jason, any thoughts about creating & posting any working drawings of this?  :stickpoke:

 John

Offline Jasonb

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Re: Little Wall
« Reply #19 on: April 16, 2022, 07:40:39 AM »
You would not want to see my working drawings :-[

I tend to model it in 3D and then just take off the sizes I need on a quick hand drawn sketch for the manually made parts, CNC cut stuff does not need a drawing. Funny enough it seem from a recent thread over on ME that quite a few people do similar. These are the "working drawings" for the engine I've just completed :)



Though if you are able to open Alibre files or split the individual components from a STEP file then I can post those

Online Jo

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Re: Little Wall
« Reply #20 on: April 16, 2022, 07:48:48 AM »
You would not want to see my working drawings :-[

You have been working with Alyn Foundry too long  :lolb:

Jo
Enjoyment is more important than achievement.

Offline Jasonb

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Re: Little Wall
« Reply #21 on: April 16, 2022, 07:55:17 AM »
Yes there are those of us who intuitively seem to know what's required and don't need a fully drawn up set of plans. Though I will produce them for any designs I publish and maybe his too.

He's been sending me more fag packet sketches and some of his old etchings recently and asking about patterns, I'm sure it's a ploy to get me to like castings :disagree: ;)

Offline Jasonb

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Re: Little Wall
« Reply #22 on: April 16, 2022, 07:30:51 PM »
The engine has a rather shapely combined inlet and exhaust manifold that would have been an aluminium casting on the original and is an ideal candidate for CNC machining as that handles the curves very well. The passage s would have been cast in using cores and I did toy with the idea of making in two halves in brass so the passage could be milled out and then solder the two together. In the end I worked out tat a couple of carefully placed drill holes would meet in the middle and hopefully not come out the side so a one piece aluminium part was on the cards. You can just see the orange ctr lines of the holes on this drawing together with their depths and angle of drilling.



A block of 6082 was machined to overall size and held in the vice to first rough out to half depth using an adaptive tool path using a 4mm flat ended 3-flute cutter. I'd put all the holes in earlier while it was an easy to hold rectangular block

.

Then the "steep and shallow" path was used while I still had access to refine the shape. I think that was a 3mm ball nose 4-flute cutter but may have been 4mm.



It was then put back into the vice the other way up and a mirrored version of the CAM used to complete the other side as the top and bottom flanges are different shapes.



I'm quite pleased with how it came out, probably should have run a "pencil" path that has the ball nosed cutter run along all the internal fillets which would have got rid of the slight steps.



I spent a little while smoothing this and the crankcase casting with needle files and then had a go at bead blasting them with a very basic Aldi spot blaster which gave the desired finish but I need to get small cabinet as glass beads on the garage floor can be a bit slippery ;D



A couple of photos of the engine coming together taken prior to the bead blasting to round things off for tonight.













« Last Edit: April 16, 2022, 07:36:42 PM by Jasonb »

Offline rklopp

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Re: Little Wall
« Reply #23 on: April 17, 2022, 06:04:02 PM »
This setup seems sketchy. (Photo of part in vise after machining second side.) Did you not have any support underneath the part?

Offline Jasonb

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Re: Little Wall
« Reply #24 on: April 17, 2022, 06:36:00 PM »
I don't think I did have anything as it was a while ago that I did it, though could have been a packer under the rectangular flange.

Offline Jasonb

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Re: Little Wall
« Reply #25 on: April 21, 2022, 07:32:02 PM »
The crankshaft started life as a length of EN8 round bar and was reduced down to a rectangular section using a 5 insert face mill regularly flipping the bar over to minimise the risk of any distortion caused buy taking a lot of metal off one face in a single go.



I then used an angle plate and 20-40-80 block to give me two reference faces to clamp the now rectangular bar to so that the ends could be centre drilled ready for subsequent turning



To avoid the knock, knock, knock of the interrupted cuts I milled out most of the waste between the webs with a 10mm cutter



Over to the lathe and a soft ctr held in the 3-jaw was trued up and the chuck jaws also work well to drive the dog. I use a GTN2 insert that has been modified with a Dremel cut off disk to remove the cutting edge in the middle to do the last few finish cuts moving the tool from side to side



After milling away the waste at either end and fitting a packing piece between the webs the shaft was turned down to the required 10mm diameter 8mm diameter and the ends reduced ready to be threaded M6. The shaft was then set aside until the flywheel and pulley were ready so all the tapers could be cut with the top slide at the same setting.



With the shaft diameters finished I could use that as a gauge to bore the bronze bearings which are just simple flanged ones



There are bolt on counterweights on the crank webs, I started by turning a piece of bronze.



Then milled some slots to produce the two "half circle" weights



And then a slot to fit over the crank web's end and a hole for the retaining cap head screw



A couple of shots of the crankshaft with it's weights and the bearings one of which is fitted to an end cover.






Offline Dan Rowe

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Re: Little Wall
« Reply #26 on: April 21, 2022, 08:27:02 PM »
Nice sequence of making a crank. Is EN8 a stress-proof type of steel?

I really like the double-dogging photos, I have never seen that done before.

Cheers Dan
ShaylocoDan

Offline Jasonb

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Re: Little Wall
« Reply #27 on: April 22, 2022, 07:05:37 AM »
No it's nor stress proof hence the care taken to machine a bit of each side so the internal stresses don't cause movement, you can get it in hot rolled which should be less risk but smaller diameters >2" are usually sold cold rolled. Its a medium tensile steel but still quite easy to machine. In the US it would be 1040 0r 1045

Best not go googling for more images of Double Dogging, could certainly have a different meaning over here :naughty:

Offline steam guy willy

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Re: Little Wall
« Reply #28 on: April 22, 2022, 12:15:47 PM »
Wow this is looking really good  and the needle file work has worked really well  :praise2: :praise2:

Willy

Offline Dan Rowe

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Re: Little Wall
« Reply #29 on: April 22, 2022, 01:18:32 PM »
Best not go googling for more images of Double Dogging, could certainly have a different meaning over here :naughty:

Thanks for the info on EN8.

That last bit made me spit out my coffee laughing so really thanks for that laugh, good one.

Cheers Dan
ShaylocoDan

Offline Johnmcc69

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Re: Little Wall
« Reply #30 on: April 26, 2022, 05:50:22 PM »
 :ThumbsUp:
It's a shame that the crank will be hidden inside, that turned out beautifully!

 John

Offline Jasonb

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Re: Little Wall
« Reply #31 on: May 01, 2022, 04:46:28 PM »
Indeed it is, maybe that is why I prefer the open crank IC or steam engines where you can see a bit more of what is going on.

I did not take many photos of the flywheel being made as the process was very similar to others I have done. Basically a slice of cast iron bar was turned and bored undersize, some waste material removed on the manual mill before cutting the spokes on the CNC.



I also turned up the pulley for the starter cord and then it was safe to set over the topslide so all the tapers could be cut without disturbing it. First the two ends of the crankshaft were done.



Then the two bores. As the taper got smaller towards the headstock and the topslide was advancing the opposite way I needed to cut on the back side of the bore I needed to use  one flute of a 3 flute cutter held in the topslide which worked well fiving a taper from 8mm down to approx 7mm with a little room to spare around the 6mm dia cutter. Here you can see me gauging the size using a park on the crankshaft to get the right length of taper into the hole.



The piston was straight forward turning but I did use the CNC to form the dog bone recess in the underside as well as the shaped top, a flange type ER32 collet chuck comes in useful for these types of jobs and does nor damage or mark the thin skirt of the piston



A group shot of progress at this stage. There is also a Tufnol disc which clamps around the end of the exposed main bearing and that carries one of the ignition contacts, rotating the disc advances or retards the timing.




Offline RReid

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Re: Little Wall
« Reply #32 on: May 01, 2022, 05:29:57 PM »
Continuing to enjoy this build, Jason. That is a pretty little piston!
Regards,
Ron

Offline Zephyrin

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Re: Little Wall
« Reply #33 on: May 01, 2022, 08:16:27 PM »
Nice piston with the deflector, true vintage model !
the transfer does not seems to be piston ported ?

Offline Jasonb

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Re: Little Wall
« Reply #34 on: May 01, 2022, 08:37:24 PM »
Here's a couple of extracts from the original drawings showing the ports

Offline Jasonb

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Re: Little Wall
« Reply #35 on: May 07, 2022, 04:40:37 PM »
The carb design for this engine is quite similar to that of the Stuart Lightweight I made some time ago and I took the same approach of silver soldering a bunch of brass parts together to replicate the casting all done on the manual machines. I did however make use of the CNC to shape the fuel bulb, first roughing it out with an adaptive cut - the inside has a shallow draft angle.



And then a finishing path to tidy things up



While still in the vice the two lugs were drilled and tapped M1.6 and then used to hold the previously turned cover which was nounted upsid edown so as not to crash the cutter into it's threaded spigot. Again a roughing and then a finishing pass were used.



Here are all the parts prior to soldering the body together



Once soldered the body could be treated much like a casting and the various remaining hole sand passages added, here the throttle body is being drilled prior to reaming.



And the completed carb in bits and all assembled





I'm not one for silencers so a simple stub pipe exhaust was bent up from 8mm copper tube and silver soldered to the flange



Finally a quick trial fit on the manifold




Offline Alyn Foundry

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Re: Little Wall
« Reply #36 on: May 07, 2022, 05:39:30 PM »
Very nice work Jason. :ThumbsUp:

I can see something else that is nearing completion too !  ;)

 :cheers: Graham.

Offline Admiral_dk

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Re: Little Wall
« Reply #37 on: May 07, 2022, 06:36:31 PM »
Looks amazing Jason  :ThumbsUp: - did you use a jig to hold all the parts in place while soldering ?

Per

Offline Jasonb

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Re: Little Wall
« Reply #38 on: May 07, 2022, 06:54:00 PM »

Graham, that one has stalled a bit.

Per, I made it so it held itself together. You can see a rod coming out of the fuel bowl, that passes through several parts and had a nut on the end to pull them together and the slots keep them lined up. This rod got machined away as the passages were drilled

The angled boss for the needle fits into a hole and that in turn stops the throttle barrel sliding down too far. Finally the flange fits onto a spigot on the top of the vertical part, I left the flange round and shaped it after soldering so did not have to worry if it revolved during soldering.

I think I just wired on the small tab that the throttle lever stops bear against

Offline Jasonb

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Re: Little Wall
« Reply #39 on: May 18, 2022, 04:58:29 PM »
The conrod started out as a piece of round 2014 rod and was "squared up" on the manual mill using a facemill.



I then narrowed down the big end using the same cutter before holding the rod on end to drill and tap for the big end fixings and then used a slitting saw to cut off the cap.



I then drilled and reamed the two holes followed by milling away some of the waste so that the big end bolts could be fitted, I have then screwed in from the rod side not the cap side. Two top hat bushes were turned up so I could screw the rod to a piece of scrap and then mill to shape on the CNC.






Well that's about all the photos and video I took while making the engine. I finished it off with some Blue VHT and and black Thermacure paint with the crankcase and manifold left in the bear bead blasted finish.















Well at this point you will all be expecting a video of the engine running but it is not obliging. I can't get a decent run out of it and by the time I have picked up the video it's already dead or dying. I know some say it's all about the journey which has been quite a fun one and I also learned a lot about the CNC but can't help feeling the journey is not really complete if you don't make it to the intended destination. Once the blisters from pulling the starter cord have healed I may have another go and make an adaptor to try a RC carb but more than likely it is destined to be eye candy on the shelf.


Offline Admiral_dk

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Re: Little Wall
« Reply #40 on: May 18, 2022, 08:27:14 PM »
That is a shame and I do understand your frustration - looks really good though ....

Do you have any idea if the 'original back then' was known as a runner ?  Or could that be a reason it kind of disappeared into oblivion ....  :noidea:

Per

Offline Jasonb

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Re: Little Wall
« Reply #41 on: May 19, 2022, 07:33:57 AM »
I don't know if the original ran and have not been able to find any examples on the ned dead or alive. Though a bit of googling last night may lead to something, I'll post here if anything comes of it.

Offline Zephyrin

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Re: Little Wall
« Reply #42 on: May 19, 2022, 08:21:47 AM »
Wow, the finish is outstanding, up to the screws and studs...
2 strokes are sometimes temperamental...and yes this is frustrating
may be you are too impatient, it simply requires a break-in !
« Last Edit: May 19, 2022, 08:40:28 AM by Zephyrin »