Revving very high and unable to balance carbs

Smousley1995 · Post by **Smousley1995** » Sat Jan 10, 2015 5:20 pm

Hi, its a bit of a long one but here goes.
The bike was not starting well while hot and progressively got worse over a few weeks at christmas. When i got back home I had the bike in the house to do some work and discovered the cam chain tensioner blade had snapped (which was weird because it wasn't rattling much) so i determined that this was causing the starting problems.
While the bike was in the house I checked the valve clearances (all fine) changed the tensioner blade, coolant, oil, filter, air filter, spark plugs, and cleaned the carbs. I bought a K and N filter so when rebuilding the carbs I put size 100 main jets in and two 3mm washers under each needle as a starting point and was going to play about with things once i got it running.
Now I just started the bike after all of this (with no air box on at the moment, just open carbs) and it was idling away happily. I then started it again and the revs hung at about 4000 and wouldn't go down. I put the pilot screws in to 1 and a half turns out because i presumed it was running rich and started it again. It idled fine with no choke when i started it but when i turned it off and started it another time (with no choke) the revs rose to about 6000 and stayed there again. i managed to get it down by backing off on the idle adjuster and then it nearly stalled so i had to return the idle adjuster to where it just was but this time it idled fine.
So i let it warm up, connected the vacuum gauges and then started it again and the revs were doing the same thing. I managed to sync cylinders 2 and 3 while it was idling but when I put the tiniest bit of pressure on the screw to sync cylinder 1 and 2, the revs would rise up to about 10,000 and settle down once i backed off the idle adjuster and then returned it back to where it was. Now i couldn't even get the screwdriver into the screw to adjust them because whenever i just touched it, it would send the bike revving like mad.
Also the idle adjuster is very very sensitive, the tiniest twist of it changes the revs a lot.
I don't think it is related but to make matters worse my battery is barely holding charge so I've had to give up on account of the battery not being able to start the bike anymore.
Does anyone have any insight into why the bikes revving like mad at the slightest of things?
Cheers

JamieNeve · Post by **JamieNeve** » Sun Jan 11, 2015 6:08 am

I once had a sort of similar issue, where by tightening the carb jubilee clips onto the intake caused the bike to start revving like mad. I still am not sure what it was, but think I was catching the butterfly valve on the clip when tightening it.

Could also be an air leak, when it is idling normally, if you rev it, does it return straight back down to the idle, or do the revs hang for a bit and slowly decline back to idle?

RedexRobB · Post by **RedexRobB** » Sun Jan 11, 2015 8:25 am

While adjusting the balance screws, press down on the the throttle stop. As you adjust the screws and push on them, it opens the throttle hence it revs up.

Also, if revs are hanging it usually means its lean, not rich, hence its ok with choke,, so you want to turn the screws out iirc (there was a huge debate on this a while ago which way to turn so feel free to correct me) to richen it up. Standard is about 1.5 turns out from fully in, but with your filter, needles n jets off standard, it may need to be different n is probably the root cause of all your issues but some setup time should have it sorted.

Smousley1995 · Post by **Smousley1995** » Sun Jan 11, 2015 9:29 am

Cheers guys, I'll check if there's an air leak today before starting and try pressing on the throttle stop.
After thinking about it last night I think the raised needles might be the issue. The only differences from before I did the work is the pilot screws, needles and larger jet (the air box isn't on yet) It ran fine with the larger jet before and the pilot screws weren't so temperamental before too so I'll try remove the needles and see if I get anywhere.

Smousley1995 · Post by **Smousley1995** » Wed Jan 14, 2015 8:49 am

Turns out it was my rubbish battery. I left my heated grips on (I'm too lazy to wire them into the ignition) for a few days and after charging my battery it would hold barely any charge and only turn the bike over for about 20 seconds before it was all but dead.
When I replaced the battery it revved a lot better and let me hone in on the correct pilot screw settings.
I never knew a bad battery could cause that!
Cheers for the help.

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