wanted-valves 750 head

[jmw76]

Hi Guys,

Trying to rejuvinate a 750 head that has a few suspect valves.
Does anyone out there have a set of valves (or at least most of them) for a GSXR750 J/K head 1988/89 (short stroke, DOT head).

Peter.

[jmw76]

We might need a complete head now if anyone has one. Short stroke 750.

[hyside]

I may have one!
nobby@hyside.com.au

[DCRacing]

Hey Nobby,
If Peter doesn't take the head i would stick my hand up for it.
Email sent.

[jmw76]

Thanks Nobby.

Email sent.

[Dynomutt]

Valve size for the shortstroke is the same size as the 1100 and 1200

[jmw76]

Yes, valve head size is the same.
Stem length is different.

[03gixxerpilot]

hey Peter, just as a matter of intrest what is the diffrence in lengths.

Cheers Clive

[jmw76]

Now you are testing me.

I haven't got any valves in front of me at present.
From what I recall the 750 stems are about 3mm or so longer.

You might be able to use the 1100 valves in the 750 head. This would give a greater seat/spring pressure (if you use the 750 springs) but you would need to check the clearance between spring cap and guide at full lift and check for coil bind.

Fitting the longer 750 valves in the 1100 head would leave you with too little seat pressure I would suspect. This would most likely promote valve float at high revs.

Cheers

[jmw76]

Also out of interest.
The springs are not the same either.
The 750 revs harder and has slightly heavier valves (longer stems) and hence needs tougher springs.

[DCRacing]

I was talking with Joe Marshall a while ago on valves for the heads, he mentioned that he is using the 2nd hand valves out of the crf250? engines, as they throw them after a short run, or it is part of the scheduled maitenance. I think he also said they are titanium, not sure on the length tho, i seem to remember something about that..........
but either way he was running them
They were cheap to as they were a throw away item.

[03gixxerpilot]

thanks Peter im not going to be changing any valves etc, am just intrested

Cheers Clive

[evilkarl]

I think you will find the CRF250 valves are titanium. Great valves but will really eat into your seats in a matter of running hours. The reason they are throw away valves is because the CRF boys are only getting 20-40 hours out of an engine. They throw the titanium values out and put stainless in.

If it's any help, I have a set of 25mm stainless values for gixxer, brand new. I also have a 750 slabby head complete, near new came off a 1986 model

[jmw76]

Hi Guys,

Thanks for all that info.
20 - 40 hours out of an engine. Wow!!!

Are the 250 valves the same size as the 750 short stroke ones.

Karl, a 1986 750 head is the wrong type for us. We need a short stroke head. Hopefully Nobby's head will meet expectations (That sounds a bit sus!!!). Thanks anyway.

Peter.