Valve clearance anomaly

I just checked my valves... It verified my suspicions on why it won't hold an idle. However, my question is... Has anyone ever found one of the clearances too great? One of my exhaust measured at .24mm.

Curious,

 

Unusual, but not unheard of.

 

Oh, by the way, here are my specs....

In 1 2 3 4
shim 275 270 285 285
measure 0* .13 .12 .06

EX
Shim 275 275 265 270
Measure .12 .24 .18 .07

*= could not get .04mm under cam (.04mm smallest available)

By my calculations, I need two 260, one 265, one 270 (will remove from other), one 275 (will remove from other), and two 280 shims.

Send PM to Hogfiddles. Just waiting for return PM with availability. Then, it's to order remaining from Len.


V/R



edit: I can't seem to align the numbers correctly. My apologies...

 

PM's back..... Will check what I have tonight.

 

All valves are now in spec. Just waiting on a new valve cover gasket.

Thanks Hogfiddles

 

number one intake being too tight will cause hard starting and poor idle for sure. that loose exhaust valve is weird. either a miss adjustment by the p/o or maybe a bent valve. a leak down test on cylinder 2 would verify the condition of the valve. at any rate a quick compression test across the board would give you a good idea of where you stand.

CN

 

Well, I can say, with 100% certainty, that the valves were never checked prior to now. My grandfather purchased it new in 1981. My father gained possession of it in 1995. And in 2007, when I acquired it, it only had 3800 miles on her. I will admit, I should have checked them long ago. At least I had the smarts to mothball it and not ride it after I started having idle issues with her. I will do a comp test after I get the valve cover install.

 

Ok valves in spec... Valve cover installed... Now carbs WAY out of whack. Spend a couple hours trying to get it to idle. Pulled carbs to check for cleanliness. Good to go, no clogged jets or passageways. Installed carbs and vac-synced motor. Still not holding idle. Started adjusting idle fuel. Finally was able to get it to idle. However, screws are now 5.5 turns out. Looks like I've got some jetting to do. My previous tuning was all in vain due to out of spec valves.

Lesson learned!!!

Gotta pull the valve cover off again due to the half-moon shaped cam plugs started leaking now.

Looks like I have a few more hours of work ahead of me before it is road-worthy again.

 

Just curious, with the idle adjuster,is there a set "baseline" of how many turns out if the bikes' stock and everything is running good? I understand it most likely varies with a lot of people an individual bikes but wasn't sure if Yamaha had a "baseline" for it.

 

Its 30 years old. Have the throttle shaft seals been replaced? I'm a firm believer in stepping the low speed jets up one size even with a stock air box but I'd change those shaft seals before thinking of re jetting. 5 turns out tells me there is air leaking in there somewhere.

 

The only "baseline" adjustment that Yamaha publishes is 2.5 turns out on the pilot mixture screws for the Hitachi equipped bikes. And it's only in some of the manuals, not all.

The actual idle adjustment is linkage-related (as is carb sync) so there is really no way to establish a similar "standard" for those adjustments.

 

Shaft seals are good. The need for rejecting is outlined in a post that I contributed to a while back, when I added pods. I wish I had verified my valves bact then. Needless to say, none of my jets(fuel or air) are stock at the moment. My plan is to lower the air jets to get me close to ideal. I'm already running with #41 pilot fuel jets.

Take heed to what everybody says about verifying that your valves are in spec BEFORE tuning your carbs!!!!