Engine advise please

If it's broken or just needs tweaked

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Riche
Posts: 19
Joined: Fri Sep 22, 2017 5:27 am

Engine advise please

Postby Riche » Sun Dec 17, 2017 10:43 am

Hi, So I did compression test on my cb650:
Results were:
1: 140 psi
2: 90
3: 75
4 90

The story was this engine was rebuilt by a Yamaha tech....
so I have taken off the head and it’s now on the bench with the chambers filled with diesel to see if the valves are leaking. To be fair they don’t seem too bad.

I have been inspecting the pistons and rings which I have a few questions about.
According to the manual the top ring is has this profile [] and the lower ring is like [\ but my top ring has have a chamfer on the top of the ring they are also marked R & RN my feeling is the rings are not on the piston in the right order. I have checked the ring gaps which are 0.30 - 0.40 so we’ll in tolerance.
Can anyone enlighten me on the rings?
Thanks

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GeorgeSweety
Posts: 222
Joined: Tue Aug 08, 2017 11:47 am
Location: UK.

Re: Engine advise please

Postby GeorgeSweety » Sun Dec 17, 2017 11:49 am

Hi Riche, its been a while since I took the barrels (jugs) off of my Nighthawk but I haven't touched the pistons or rings yet so can't speak from experience but this link may help.
http://www.duncanracing.com/TechCenter/ ... -24-05.pdf

If that doesn't help I'll go in the shed tomorrow with my camera and check on mine, see what's what :D

Riche
Posts: 19
Joined: Fri Sep 22, 2017 5:27 am

Re: Engine advise please

Postby Riche » Sun Dec 17, 2017 2:53 pm

Thanks George your a star, so it does look like the ring have been put on the piston in the wrong order. As for the rest of the bike it’s still n progress. Welding, painting all done but the engine and carbs have been the thorn in my side. Still have quite a lot of wiring to do and am still n the look out for a front mug guard. But making progress.

I missed your message, How are you getting on?

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GeorgeSweety
Posts: 222
Joined: Tue Aug 08, 2017 11:47 am
Location: UK.

Re: Engine advise please

Postby GeorgeSweety » Mon Dec 18, 2017 12:03 am

Hi Riche and thanks, I'm happy that I could help :D I haven't fixed (or broken) anything in quite a while as I've been sorting out a shed to work in, I'm getting too old for kneeling on concrete :(
I was going over your thread the other day as I've bought a CB650Z engine, carbs, frame and forks that a previous owner was going to Cafe, well he sawed a few bits off the frame that is :roll: so I was just exploring my options. I still have the original spoked wheels from my 650 Custom so I've got the basis for a Cafe project if I stuck it all together. But I'm more into Custom or standard bikes, plus I've got enough to do already :lol:

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GeorgeSweety
Posts: 222
Joined: Tue Aug 08, 2017 11:47 am
Location: UK.

Re: Engine advise please

Postby GeorgeSweety » Mon Dec 18, 2017 1:01 am

Riche, PM sent.

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Folsoml
Posts: 1488
Joined: Sat Apr 07, 2012 9:02 pm
Location: North Florida

Re: Engine advise please

Postby Folsoml » Mon Dec 18, 2017 1:17 pm

Hey Riche! I can't see your pictures.
Have a problem with your CB650? Have a technical question? Click here!


My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

Riche
Posts: 19
Joined: Fri Sep 22, 2017 5:27 am

Re: Engine advise please

Postby Riche » Tue Dec 19, 2017 7:08 am

Hi George,
Your 650 project sounds awesome.. I wish I had the wire spoked wheels, I think they look so much better ...
I try to upload some photo's soon..

Rich


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