Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: philward on April 16, 2016, 06:17:20 PM
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Just stripped the engine I have for the CR750 project. Overall everything looks good - ie mains and big ends. So will be replacing normal cam chain train parts (with original genuine Honda rollers/etc), primary chains, valve springs, etc. I havn't measured the bores/pistons yet but look ok and envisage that I'll either be just changing rings or maybe next size rebore.
Question to everybody is:- What make of rings would be a recommendation? I seem to remember Trig saying don't use genuine Honda due to oil control ring design being inferior to good quality proprietary makes. I have a 836 Cruz Image kit on my standard K2 and all well at about 800 miles (Hondaman on US site commented that they where ok - which was why I bought them at the good price).
Also, what make of valve springs?
May need more bits when I start mic-ing up bits but I know the above would be the minimum.
Any views much appreciated
Phil
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I am using OEM but, not with the single oil ring, cruzin and rings supplied by IMD at the moment.
The engine must of done some work to need valve springs.
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Graham
I'm just assuming it needing valve springs - havn't stripped head down yet but just doing pre-buying research.
Ref pistons - what your proffesional opinion on IMD pistons?
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I bit pricy compared to Cruzin that do a full set for the price of a set of rings from IMD. Never had any problems with cruzin or IMD.
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Cheers Graham
Sent from my MotoG3 using Tapatalk
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Graham
I'm just assuming it needing valve springs - havn't stripped head down yet but just doing pre-buying research.
Ref pistons - what your proffesional opinion on IMD pistons?
I always check the free length of valve springs is within spec in manual.
There is an arguement that parts that have little or no appreciable wear and have given good service are a better bet than repro parts.
The exception is rings and rubber parts
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Now measured everything up - bores within tolerance but glazed, pistons have a few light marks but are all well within genuine Honda workshop manual tolerance figures. Head and piston crowns have lots of 'damp' carbon build up.(could have had oil down bores in storage soaking into carbon?) I bought the engine from a guy who said it was 'running sweet' but don't know the mileage. So now I'm looking at the options - do I just change the rings for genuine Honda or go oversize with a Cruz Image full kit - or even go for 836 kit from them? (As my K2 I'm running has same 836 kit on and its working great after 800 miles - with improved bottom end torque).
With my last rebuild on my standard K2, the bores where goosed so I didn't need to consider the above - had to go oversize. Just pondering this time as have the choice and obviously quality original Honda pistons still serviceable - but for how long?
Probably thinking to deep - but would appreciate opinion from fellow forum experts
Phil
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Depends what the bores are like after you mic up, if with in spec, cross hatch and new rings ;)
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Already calipered them up Graham and at top and bottom (havn't got cylinder gauge for middle measurement) they are within tolerance - as are pistons. Just concerned at carbon build up - which comes off really easy be the way.
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Cross hatch with new rings, if all is within spec.
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500 manual gives valve free length and load/deflection rate so easy to check if ok to reuse