Author Topic: 30cc Flat Four (Puma)  (Read 25359 times)

Offline Brian Rupnow

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Re: 30cc Flat Four (Puma)
« Reply #120 on: August 23, 2019, 01:33:37 PM »
I do the same test by modifying a sparkplug to take an air hose and pressurize the cylinder.--Brian

Offline Vixen

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Re: 30cc Flat Four (Puma)
« Reply #121 on: August 23, 2019, 01:55:47 PM »
Hello again Pete,

If you cannot easily find any 1200 grit  abrasive powder, it's not a problem.

Just PM me with your postal address and I will air-mail a small quantity down to you.

Cheers

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Jasonb

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Re: 30cc Flat Four (Puma)
« Reply #122 on: August 23, 2019, 02:23:49 PM »
I tend to use 1000g SiC with a drop of oil as the carrier.

Always prefer to try and do my valve guide holes and then taper turn the seats in one setting on the lathe and have not had to use a seating tool on any done that way.

Only one I did have problems on was where the valve seat was on the far side of a cylinder accessed through the inlet of the CI cylinder.

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #123 on: August 23, 2019, 10:45:39 PM »
Hello Pete

If you do an e-bay search for '1200 grit powder', you will get hits from all over the wold. UK, USA, China, Ukraine etc. It's often used by gem stone polishers.

It may be better to wait for the good stuff to arrive by post than to carry one with the wrong stuff.

If the valves are almost sealing, it may be better not to use the seat cutter again, just use the 1200 grit made into a paste with a little oil.

Mike

Mike

Thanks for the offer, 100grams on order from China. China has free shipping and the USA charge more for the shipping than the product

regards

Pete
« Last Edit: August 23, 2019, 11:38:46 PM by doubletop »
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline Brian Rupnow

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Re: 30cc Flat Four (Puma)
« Reply #124 on: August 23, 2019, 10:56:30 PM »
Pete--I use 600 grit aluminum oxide paste for lapping my valves. If I think the 600 grit isn't going to do it, I lap first with 400 grit, clean everything well, then use 600 grit. I have never used anything as fine as 1200 grit.---Brian

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #125 on: August 23, 2019, 11:51:59 PM »

Pete--I use 600 grit aluminum oxide paste for lapping my valves. If I think the 600 grit isn't going to do it, I lap first with 400 grit, clean everything well, then use 600 grit. I have never used anything as fine as 1200 grit.---Brian


Brian

I have been using Holts fine paste; however, I can't find any technical data that tells me the grit size. As I'm almost there I'm hoping that the finer paste will do the trick.

I think the key is patience. I had on cylinder that was markedly worse than the other three. After I used my pressurised jig it was the best, so I did the others which then came out better. So back around the buoy again. That’s todays job while I wait for the 1200 grit to arrive from China. Which could take a few weeks. (I did think that if I ordered aluminium oxide powder it could attract some attention at customs  ;D)

Pete
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline Brian Rupnow

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Re: 30cc Flat Four (Puma)
« Reply #126 on: August 24, 2019, 01:27:33 AM »
I think you'd have been okay with the feds. Aluminum oxide is a widely used and distributed lapping compound. It is sold premixed with either a heavy grease or wax. (I'm not sure which). When I first started building i.c. engines, I bought a small jar of "valve grinding compound" from an automotive supplier. Compared to 400 or 600 grit lapping paste, the particles in that automotive stuff was like boulders. It was no good for model engines. I have also heard of people using BonAmi scouring powder and toothpaste. The problem with the really fine compounds is that they don't cut enough to properly lap lathe turned valves into lathe bored seats. This is all stuff learned by experience. I have about a dozen steam engines and 20 different i.c. engines.---Brian

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #127 on: August 24, 2019, 10:29:31 PM »
Brian

As I said in your thread you always seem to be successful with your engines and that’s no doubt after the experience of making twenty. This is my third and the other two ran but I wouldn't say they were fantastic runners. They took me ages to get them to start and even when they were runners the throttle needed to be opened quiet carefully otherwise they stalled.

I'm hoping for better results this time. The fit of the pistons, using O rings rather than CI and spending more time lapping the valves, the engine seems to have better compression at this point than my early attempts. That, coupled with four cylinders rather than one or two, I’m hoping that at least one cylinder will play ball and its mates follow along.

Pete
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline Stuart

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Re: 30cc Flat Four (Puma)
« Reply #128 on: August 26, 2019, 04:36:26 PM »
Any one tried “Time saver” ?

I use it to bed in bronze bearing , big ends and sutch

Yellow for non ferrous green for ferrous

The beauty is that it’s pumice based and the longer it’s used the finer it gets

Used in industry to bed in large gear boxes you bout have to dismantle/flush out

It’s also in the breakin oil in your car from new

Not connected with the firm at all just a user
Stuart

My aim is for a accurate part with a good finish

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #129 on: August 27, 2019, 07:47:30 AM »
Hi

Loosing the plot here making edits to my recent post I have over written this post. So the original post here has gone missing. Sorry about that

Making mistakes seems to be getting worse recently.

Pete
« Last Edit: August 30, 2019, 09:21:39 AM by doubletop »
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline Stuart

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Re: 30cc Flat Four (Puma)
« Reply #130 on: August 27, 2019, 10:26:22 AM »
I bought both colours they came as a trial pack with four grades each down to very fine

The metal tubs it’s in are about 40 mm dia 30 mm high

It’s a dry powder I mix with light machine oil as used on the lathe nuto32

Glad you found more info as posts are a chore when my dyslexia has a bad day ,Evan simple words look wrong and in a strange language it hard the describe how it looks , a good day it’s fine

Stuart
My aim is for a accurate part with a good finish

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #131 on: August 27, 2019, 11:07:37 AM »
Unfortunatley I can't find any reference to any suppliers of it in NZ. The top Google searches give me more links to Holland than NZ

Pete
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #132 on: August 30, 2019, 08:05:27 AM »
A bit of an update

The two ignition units arrived from China on Wednesday. Hooray!!



As they are from Aliexpress they needed to be tested and reciept confirmed. With AliPay the vendor doesn't get paid until you OK it but, once you've done it, that's acceptance.

So the first one out of the bag and connected up for a quick test.

[youtube1]https://youtu.be/23b5Zpl5_8Y[/youtube1]

Then the second one out of its bag



Only one HT lead. Damn!!

Check the bags again. Yes both RCexl 1222 twin 1/4x32 units.



So now its onto the Aliexpress disputes process. So far the vendor is making the right responses. I buy a lot of stuff from China and on balance have had a good experience and if there have been problems they have been satisfactorily resolved. However, I have recently had one major issue with a vendor selling through Ebay that took three months to resolve. A case of once bitten twice shy.

In the meantime, I have started on the flywheel and inlet manifold. No pics of the flywheel yet



There is a bit of a saga with this but I'll save that until I've got the job completed.

Pete


« Last Edit: August 30, 2019, 09:11:56 AM by doubletop »
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline doubletop

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Re: 30cc Flat Four (Puma)
« Reply #133 on: September 02, 2019, 10:20:06 AM »
I’ve now got most of it done and trial assembled ready for a bit of fettling.







I set the valves tonight and will do the ignition timing tomorrow. As it’s club night on Wednesday I’ll just be tidying up a few other odds and ends rather than trying to run it as things start to get a bit messy once oil and fuel are involved. Anyway, I don’t have the second ignition unit yet. The AliExpress vendor has given me a tracking number for the replacement so hopefully it will be in the system and on its way soon.

Pete
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline Brian Rupnow

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Re: 30cc Flat Four (Puma)
« Reply #134 on: September 02, 2019, 01:19:01 PM »
Lovely job on those copper intake runners.---Brian

 

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