Peter Day

Yamaha FZR750R OW01  & YZF750 specialist

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Forum Home > General OW-01 Discussion > OW-01 YZF750 piston & valve intechangable ?

Mark Pav
Member
Posts: 12

Is there any reason I cannot use YZF750 pistons, rings and valves in an OW-01 motor. My intuition says it should be OK. Is there something I'm missing ?

January 17, 2017 at 10:47 PM Flag Quote & Reply

Rich
Member
Posts: 157

They are all different. The valve angle is different on OW compared to YZF.

I think the OW valves may be a different length to YZF, I'll let someone else confirm it but I'm sure they aren't interchangeable.

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January 18, 2017 at 5:20 AM Flag Quote & Reply

Mark
Site Owner
Posts: 238

Mark Pav at January 17, 2017 at 10:47 PM

Is there any reason I cannot use YZF750 pistons, rings and valves in an OW-01 motor. My intuition says it should be OK. Is there something I'm missing ?

Hi, sorry, no can do. Like Rich says, the valve angle is different, and the valve pockets in the pistons are in a different place. Hit that starter and you will have some expensive scrap to weigh in.



January 20, 2017 at 4:02 PM Flag Quote & Reply

Mark Pav
Member
Posts: 12

I suppose 1989 FZR1000 EXUP pistons should be OK with regards to valve angles and positioning of cut out disregarding the obvious 3.5 mm diameter difference., there should even be a bit of a margin of error given that the FZR1000 valve is bigger. I am trying to rehabilitate an OW-01 smoker.....

January 20, 2017 at 11:44 PM Flag Quote & Reply

Mark
Site Owner
Posts: 238

Hi Mark, I'm afraid that won't work either. Your best two options are a yzf head and pistons, or a rebore and fit oversize pistons. We have yec race kit ow pistons available in 0.25mm oversize. Don't forget that if you're on original 2 ring pistons they do smoke as a matter of course. If your bores measure up within tolerance you could of course hone and fit later 3 ring pistons to cure the smoking habit. We have these too. I hope that helps.

January 21, 2017 at 3:13 PM Flag Quote & Reply

Pecions
Member
Posts: 9

Hi guys,

(the "captcha v1" system isn't working anymore, so it is impossible (at least for me) to start a new tread).

I'm looking for a new pistons set for my YZF 750 SP.

They are no longer available from Yamaha.

Cosworth has a kit they say fits the YZF but it is for the OW-01 and connecting rods from OW-01 are required (piston pin is 18 instead of 19mm).

Do you know where I can find something? Neither Wiseco nor Cosworth or other sellers I asked to seem to have anything for this engine.

Is the 850cc big bore solution my only option?

I wanted the bike for racing in 750 category, so the 850 wouldn't be a fair option..

Thank you in advance!


August 27, 2018 at 1:33 PM Flag Quote & Reply

Rich
Member
Posts: 157

Have you tried JE pistons? I actually thought Wiseco still made them too. Another option would be to get some made, there's a company near me who does it and they are surprisingly not as expensive as you'd think. Then you could go for a flat face valve design too.

Of course Peter may have some so it may be worth a call or asking Mark.

Why do you want to change them?

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September 2, 2018 at 6:19 AM Flag Quote & Reply

Pecions
Member
Posts: 9

Thanks for suggestions, but JE and Wiseco seem to have nothing for the YZF, at least on their webpages.

I wanted to change pistons because I'm rebuilding the engine for race and look for best performance. The engine was smoking tons of oil, very low compression in cylinder 1 and 2 (around 6), and damaged cylinder 1 sleeve (probably for oxide produced by water leak). So new pistons and rings seemed a good idea, in addition to rebuilding the head and replacing the cylinders :)


September 2, 2018 at 8:50 PM Flag Quote & Reply

Rich
Member
Posts: 157

Although ring wear and cylinder damage cause oil use, so do the stem oil seals. Also l find that loss of compression can be down to valve wear and no clearance, although I agree that your no 1 cylinder was probably due to the damage.

If you can't get the pistons then just go for new rings. Have a good look at the valves too, common to find them worn.

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September 3, 2018 at 8:14 AM Flag Quote & Reply

Pecions
Member
Posts: 9
Thanks Rich. The head has been completely rebuilt now. I mean deep ultrasonic cleaning, valves and seats rectified. New seals have been already installed. It is noteworthy that valve clearance before the rebuilding was a bit under the minimum for some valve, but not specially those of the two low-compression cylinders.. About going only for new rings, I've been told that at least in the ow01, the pistons got wored, specially the rings' seats, so changing only new rings could not be enough. I don't know if this is true and if is valid also for the yzf.. Anyway, apart from being necessary or not, I'd be glad to have new high compression yec pistons ;) By the oher hand, the head was lowered 0,25 mm, the cylinder is going to be lowered around 0.1. I found yec head and cylinder gasket which are supposed to be thinner, but don't know their measure.. should I worry that all this may result in too high compression?
September 3, 2018 at 7:52 PM Flag Quote & Reply

Rich
Member
Posts: 157

Make sure you have enough piston to valve clearance. The YEC pistons might be designed to use with YEC valves.

I don't think too high compression will be a problem.

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September 4, 2018 at 10:37 AM Flag Quote & Reply

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