[NC29] CBR400 lost compression

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vinibali
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[NC29] CBR400 lost compression

Post by vinibali » Tue May 29, 2018 3:39 pm

Hello there!

My girlfriend's Honda was so problematic in the past year. During these period the bike has been in 3 different services, because of difficulties at the engine starts. So she had to buy a renewed generator coil and 4 spark plugs, but the bike was still unreliable. The very first guy used to start up the engine with brake cleaner, when we said that the bike is still a ****box after giving him a lot of money (according to the wages in Hungary).
It has been about two months, when we were able to find such a great local mechanic. He said that the compression is lost, the bike probably ended up having possibly bended valves in the 1st and 4th cylinders (he said) and one of the ***holes stole the shorter air funnels from the side carburetors.
In the first weeks the engine started easily and was so powerful, didn't really show any sign of mechanical problems.
It's nearly impossible to find an NC29 cylinder head in good condition, I found two in eBay. I thought maybe the other naked 400s, like CB or Super-Four has the same cylinder head or maybe valves, which we can exchange.
Have you ever been in such a situation? :pray:

Thank you

CB1pod70
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Re: [NC29] CBR400 lost compression

Post by CB1pod70 » Wed May 30, 2018 1:24 pm

The cylinder head castings are a different shape on the CB-1 to the NC29. The CB-1 uses a lug cast into the head as a top mount whereas the NC29 uses a mount on the barrels for the top mount. The cam covers are a different shape too.
The Super Four is different again as it uses a timing chain rather than gears to drive the cams.

I've never tried it but think the valves are the all the same though if you just need to replace the valves.

just4kicks
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Re: [NC29] CBR400 lost compression

Post by just4kicks » Wed Jun 06, 2018 10:50 pm

I had a very similar problem, check my YouTube channel. It was on cold start, and while engine D warming up the accelerator was non responsive. Did some research here n sent to the mechanic to have the valve clearance checked. He also said I lost compression and I said that is due to valves not closing properly so almost no compression for engine to swing. He replaced 3 shims on intake side, cylinders 1;3 and 4 and now all is right again.

vinibali
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Re: [NC29] CBR400 lost compression

Post by vinibali » Wed Jul 18, 2018 3:07 pm

thank you guys.
just4kicks: please share the link.


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