R65 over revving problem

Hi all, Aaron (who I work with) has recently bought an R65 (electronic ignition model, not the one with the ‘bean can’).

The bike when warm over revs quite badly at standstill and I think the RH carb is over flowing with fuel leaking out the float bowl.

Initially thinking it was the float needle valve not seating correctly (and thereby not stopping the flow of fuel into the float bowl) I replaced the needle valve and for good measure the float too (just in case it had lost its buoyancy).

This hasn’t stopped the problem so I’m wondering if anyone could offer any advice and things to look at?

Thanks.


Sent from my iPhone using Tapatalk

HI Mark

There are a number of things that can cause this, so a few basics first (not an exhaustive list)

When you say over revving you meant ticking over to fast? Over revving is something else!

When you say overflowing, how much ? - lots or just a moistness around the bottom of the RH carb? (a slight dampness is not unusual). Has the LH carb been checked?

If you have replaced the valve and float, did you re-set the float height?

Air heads are quite sensitive to correct throttle cable adjustment, and balance between the cylinders.

When was it last serviced? Valve clearances can have a significant effect on idling/performance - the rule with airheads is do the valve clearances first, then everything else from there (yes, including carb tuning)

Have there been any modifications from stock set up, if so what?

Depending on age/service life/lack of maintenance etc it could be that both carbs are due a refresh/rebuild....

Im sure others will chime in.....

Marc

Thanks fella, really appreciate it - I’ll pass it on.

To answer your questions

Yes it’s over revving

It’s over flowing quite a bit - more than just moisture.

Valve and float replaced but no, didn’t reset the float height.

I followed the Haynes guidance on the cable adjustment but haven’t balanced the carbs tho I do have some vacuum gauges to do so.

It’s had a recent service but I don’t think it was anymore than just fluids and filter.

I can’t comment on the valve clearances but that’s a damn fine suggestion!


Sent from my iPhone using Tapatalk

OK, sort the leak out first - sounds like float level to high, or maybe your replacements need looking at again. I would check both LH and RH float heights while you are at it, best to confirm both carbs Ok rather than just one as the other can throw out the result....

Set valve clearances (stone cold) check/adjust cables, go for 20 min run, then start tuning after that - check cables again, balance/idle speed next then mixtures - you will have to go round a few times to dial it in to the sweet spot.

Dont set the idle too low (a common fault) as it can make balance and mixture settings skew a bit and you end up chasing shadows.......somewhere about or just below when the charge light starts to flicker off is usually about right but play it by ear...

Also worth considering that sometimes ignition timing can be an issue, stuck bob weights can give high tickover symptoms but that does depend on what system is there - fully electronic should be OK, but if its a hybrid system (like the old BMW bean can - ie electronic triggering but mechanical advance) this is a know issue from time to time...

As above, major cause is lack of play in the throttle cables 2- 3mm