Very strange!!!!!!!!!!!!

Hi all,Well been out on the bike today after a costly rebuild and was great:ride:.I reset all valve gaps to speck.But after just on day there tight again:banghead:Im down to a 1.47 r intake,1.77 l intake,1.97 l exhaust,2.02 r exhaust.The valves were taken out to have stem sills fitted and a gen decote.I ran the fresh motor letting it warm up and cool down on the stand first couple of runs,then checked the gaps and all was good.Run the bike in at the track runs great and started first kick hot or cold all day.Get home clean and a general check over bike and the intakes are tight:banghead:Naw i ride pretty hard but im no bubba.Any idears guys.Is it just time to change the buggers?cheers lee

When you say valves were taken out to fit new seals and decote, did you replace them??? The stock intakes are titanium with a hard coating. Once they start to move, they don't stop. If they were not moving before the rebuild, your mechanic didn't lap them did he? The Ti valves can't be lapped, even a little bit.

What was the reason for the rebuild and what all did you have done????

Main bearings and conrod thrust washers went and destroyed oil pump and both cases,piston.Before the motor went out for its rebuild the left intake went to zero and right was .002".As i stripped the motor partly down and out the bike to save money,i saw the valve faces and the crap on them and said to decoke them.He said he took valves out cleaned and also new stem seals were fitted.He did say in past chats that they are titanium intake valves.So must no not to lap them in.When they are worn do they really go south that fast?Think the shims needed to give the correct gap are to small and asking the valves to fail.Dont no if im over thinking this or im on the right track.Thoughts pls lads

Nope, intake valves are toast if they zero'd before the rebuild. It's not the seals that make them go south, its that you have worn the hardened coating off of the Ti valves. Pull the head back off and get it done. AT MINIMUM new intake valves. Have your machinist clean up the seats and you CAN go back with new OEM valves. I would recommend replacing them with SS valves, as they will last much longer. Changing to SS valves requires new springs on the intake side. Several companies offer the intake kits for the 250s.

If you go with SS they can be lapped. If you replace with Ti valves, NO LAPPING AT ALL!!!!

What sort of time you guys getting on ti valves?I do like the way ti valves almost tell you there on there way out with all the shiming,As with ss i read they just snap.But what sort of time would i get out of ss.Im forever pottering about with bike and keeping it in tip top nick.:thumbsup:

Hard to say. Depends a lot on how you ride and how careful you are about dirt getting through the filter. A guy that putters around on trails and cleans the filter a bunch may get hundreds of hours. A teenager who bounces the rev limiter on every shift might get 20 hours.

I think the general consensus on the Ti is 75-125 hours, when well maintained. The SS properly set up seem to go about double that (or more). I have never heard of a SS valve snapping. Not saying that they don't, but I have never seen it. If you keep shimming any valve as the face dishes, it will eventually get thin enough the the edge will chip. That chip floating around can do some damage.

Some of my fav tracks i ride im only in 2nd/3rd gear,and end up on the rpm limit as theres just not enough time or track to change into next gear.So prob hard on the motor.Filter is always clean and oiled.I have bought crf r rear numberboard plastics though,so the left airbox opening side of the box dont seal perfect so some dust is getting in there as had to cut to fit.Do you think my intake shim sizes at top of page are to small for one more shim?cheers all

Do you think my intake shim sizes at top of page are to small for one more shim?cheers all

Hi Speedy :thumbsup:

You can shim the intakes all the way down to 1.20, we have a 450R with a 120 shim fitted, it starts 1st kick every time and the next time it closes up we'll need to have the seats re-cut and will probably instal SS inlet valves instead of Titanium.

Ian :thumbsup:

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now