Jump to content
Sign in to follow this  

Speaking of valves. . .

Recommended Posts

Went to our nice groomed track for a day of riding today. Bike cut out and died before I finished my first lap. Seemed to be not getting fuel, and acting like it was flooded at the same time! It would barely kick over and die only with a handful of throttle. Changed the plug, nothing. Swapped ignitions, nothing. Checked carb, nothing. When the bike was cold, it would start, run, start to pop and bog and die. I suspected valves, because I recently stuck in a new head, springs, stainless valves, port work, etc. from RHC. So, went home and found my two exhaust valves needed 3 shims sizes bigger, and one intake valve needed 1 size bigger. Bike ran great afterwards and started first kick everytime. I never had valve issue before, so is this what happens when your valves get out of spec? I guess I needed to check my tolerances after break-in which I had been putting off. . . :)

Share this post


Link to post
Share on other sites

Amazing how much better these bikes run when the valves are in spec :):) .

696

Share this post


Link to post
Share on other sites

I installed my new head with RHC SS valves and HD springs in September 04. I rode the bike for about 3 months without checking the valves. The bike started and ran great all 3 months. I only checked the valves in December because it's winter here in PA and too cold to ride, so it was time for maintenance. My exhausts were spot on at .011, and my left intake was at .005 and my right intake was at .0035. For all I know, my intakes lost that much clearance within the first 2-3 rides. RHC said it's typically in all new heads/valves to lose about .002 during break in.

Share this post


Link to post
Share on other sites

I just did the intakes on my 03 with stock valves and the left side valve was cupping into the head. The power difference between the beat to crap valves with proper adjustment and the new ones with seats cut in for the m and properly adjusted was night and day difference. The bike runs awesome. But do you know if it is after 5 hours or after 10 hours for the first adjustment? Its amazing the difference in power. :) Its like a new bike.

Share this post


Link to post
Share on other sites

I received my new head in December and due to weather have only ridden it twice a month since. I have never checked the valves until now, so I assume just about 2-3 months of casual (but hard!) riding is about enough time to re-check your tolerances.

Share this post


Link to post
Share on other sites

you should not have had to put larger shims in to take up clearance they should have been smaller to open up clearance .

Share this post


Link to post
Share on other sites

Gee, I hope nothing's amiss here. . . went from 235's on the exhaust to 245's, one intake went from a 150 to a 155, the other intake was okay. Bike ran fine today, no problems. Just a little more finicky to start. . . My two exhausts measured .381, one intake .178, and another .229. Can you damage your head by running with loose valves? I barely got it started with my out of spec valves, but did get 2 laps in before the thing refused to start. When I did start it, it coughed, popped and sounded like it was running really rich. The bike ran and started fine today, so you think I'm in the clear? :)

Share this post


Link to post
Share on other sites

My guess would be that your cam timing was off from the start and when you went back in to re-shim you got it right when you put it back together.

I've run valves about as loose as you did until I got the right shims and didn't have any problems other than some valve clatter once it warmed up.

Either that or the cam jumped time after your 1st put it together (maybe even in the 1st few kicks) and you got it reset when you re-shimmed. How old is your cam chain tensioner? For some odd reason they like to fail after you rebuild the top end. I had one do it and I've heard of others that have had failures just after a rebuild.

Share this post


Link to post
Share on other sites

I don't think it can be the timing. I've been riding off and on for two months now, no problems. As for the tensioner, it appears good and my bike is only an '04. . .

Share this post


Link to post
Share on other sites

i dont think theres any thing to worry about if you did not have the ex cam lobe in the exact location when first setting the valves you may have had them loose the first time .Ron

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

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

Reply with:

Sign in to follow this  

×