Fast idle?

[unigobill]

Question? Dug out the old R90 this week to do a New Years ride (had not been started in two years) Clean every thing up, replaced a couple of o-rings in the carbs, everything seemed fine. Rode it around town 15-20 miles OK lets go. Stop for gas at about 140 miles and it was idling at 2500 rpm, filled up started and it the idle is back to normal? This repeated at each stop???

[krehmkej]

Easy things to check are:

advance weights on points are sticking
throttle cables hung up

[20774]

Did it do this before the carb work? Since it had been two years, no real way of knowing... But if not, then sounds like it's something you did (or didn't) do as part of the carb work. What o-rings did you replace? What did you do in cleaning the carbs?

Usual suspects - not warming bike up after carb work prior to resynching the carbs, vacuum leaks, hanging advance unit, hanging throttle cable barrels, air leaking through enrichener gasket, enrichener partially on.

My guess is the carb work changed some of the idle characteristics of the bike and they need to be resynched...after a thorough ride. Seems like that's what was happening with each stop...you're riding along, everything's fine, but then you come back to idle and it's too high once the bike was at operating temperature.

[orbitangel]

Question? Dug out the old R90 this week to do a New Years ride (had not been started in two years) Clean every thing up, replaced a couple of o-rings in the carbs, everything seemed fine. Rode it around town 15-20 miles OK lets go. Stop for gas at about 140 miles and it was idling at 2500 rpm, filled up started and it the idle is back to normal? This repeated at each stop???

B.B.

You didn't say whether your R90 is an R90/6 or an R90S. That may affect the ideas you might get (from those of us who don't know ya' already)...

HOWEVER...

If this were my bike, the FIRST thing I would do is pull that front cover.

You can move the advance weights with your fingers. If all is well there, they will snap right back to the "retarded" position.

My suspicicions (given how long it had been parked) are that the interface between the end (nose) of the camshaft and the bore of the advance mechanism (inside the cams for the points) is either kinda rusty or kinda gooey - maybe both.

Clean up the end of the cam with some solvent and a rag, try a Scotchbrite pad if there is rust.

Then clean out the bore of the advance mechanism, any way you can.

A little light machine oil or very light grease on the end of the camshaft will keep this critical mechanism free.

Dont forget to line up the flat on the cam with the flat in the hole (behind the 10mm nut) and do remember to lift the points as you slide that advance mechanism back on.

Don't go crazy tightening that 10mm nut either or you're in BIG trouble.

IF the advance weights "snap right back" (every time) when you pull on them (meaning that the advance mechanism rotates FREELY on the camshaft nose) then your trouble lies elsewhere - sticking carb slide, throttle cable hanging, etc.

You DO have that 4mm of free play in the throttle cables (cable housings, actually) at each carb, right?

NOTE: My little diatribe assumes that your plugs are firing at the "S" mark and not before!

Good luck!

[unigobill]

B.B.

You didn't say whether your R90 is an R90/6 or an R90S. That may affect the ideas you might get (from those of us who don't know ya' already)...

HOWEVER...

If this were my bike, the FIRST thing I would do is pull that front cover.

You can move the advance weights with your fingers. If all is well there, they will snap right back to the "retarded" position.

My suspicicions (given how long it had been parked) are that the interface between the end (nose) of the camshaft and the bore of the advance mechanism (inside the cams for the points) is either kinda rusty or kinda gooey - maybe both.

Clean up the end of the cam with some solvent and a rag, try a Scotchbrite pad if there is rust.

Then clean out the bore of the advance mechanism, any way you can.

A little light machine oil or very light grease on the end of the camshaft will keep this critical mechanism free.

Dont forget to line up the flat on the cam with the flat in the hole (behind the 10mm nut) and do remember to lift the points as you slide that advance mechanism back on.

Don't go crazy tightening that 10mm nut either or you're in BIG trouble.

IF the advance weights "snap right back" (every time) when you pull on them (meaning that the advance mechanism rotates FREELY on the camshaft nose) then your trouble lies elsewhere - sticking carb slide, throttle cable hanging, etc.

You DO have that 4mm of free play in the throttle cables (cable housings, actually) at each carb, right?

NOTE: My little diatribe assumes that your plugs are firing at the "S" mark and not before!

Good luck!

/6, I replaced the o-rings on the Idle jets, just sprayed the cleaner through the carb and then air. I did pull the advance seem a little sluggest lube it and it move free, but the springs don't hold the arms snug? I will get some new springs and try that. Thanks for all the advice. Oh the throttle carbs are new and have the required free play.