Revs don't drop (again)

[GavD]

Got the bike back together and rode it 5 miles for the MOT on tuesday, when I got to the garage it seems to be running a bit rough, turned it off and let them do the MOT, then riding home it started running rough and cut out on me. Checked fuel, managed to get it running again, then ran it home in 3rd keeping the revs high as it seemed happier like that.

Got the carbs stripped out and checked the floats/needle valves & diaphragms - they're keihins so no little o rings involved. All looked good. The carbs had been drained of fuel over the winter, as was the fuel tank.

Put it all back together and got her started fine, then as it warmed up to mid way on the temp guage I noticed that as you rev'd it the revs would gradually drop rather than come down as normal. The hotter the bike the worse it seemed.

Remembering threepots recent issues I stripped the airbox out for a look. I'm pretty sure it's the original one and it has some cracks in it around some of the screw holes, but they're certainly not big cracks. Carb to head rubbers were new about 3/4 years ago and I've had them off for inspection, all OK.

I've ordered a new airbox and the 3 rubber joints onto the back of the carbs.

I was wondering if anyone else had any other suggestions I should be looking at while I wait for the new bits to turn up?

Thanks in advance
Gav

p.s. I'm using the fuel I drained in the autumn, I'll put fresh in once I've got the airbox.

[Sin_Tiger]

You're probably in the right area but give yourself a fighting chance with some fresh fuel, you can always use up the rest adding it in small amounts later.

Worth pulling your HT leads to check the condition at the ends and making sure they snap in 1 2 3 when you put them back.

[JayDub]

I had problems with old fuel last month, use fresh stuff like Sin says, It does sound like carb/fueling and did you clean the jets?  they can still get gunked up even if you drain the carbs...I've first hand experience of the evils of Ethanol.

[GavD]

Cheers chaps,

I've not got HT leads anymore Sin, went the TT600 coil route, will check them out though to make sure they're making good contact etc.

JD, I've assumed that since I drained the carbs they'd be OK, but maybe while I've got them out for an airbox change, I'll give the jets a bit of a blow through.

Think the old fuel will end up in the lawn mower!

[Sin_Tiger]

I'd forgotten about that 

You don't do the mowing then 

[threepot]

I'm convinced my issue is since I've cleaned the k&n filter? And I've noticed that since I've turned the idle mix screws back to 2 turns out,bike doesn't start ..after initial cold start,so well? So I'm going to turn them out a little more,next chance I get. I just think that the t3..t4 engines just need to be run regularly? Just changed the oil on mine,and that has made a 'little' difference. Hope some 'fresh' juice,and a good run will sort yours?

[GavD]

You don't do the mowing then 

Only when I have to

[nickjtc]

I'm convinced my issue is since I've cleaned the k&n filter?

You didn't over oil it, did you? I did that once and the bike it was on refused to run well.

[JayDub]

JD, I've assumed that since I drained the carbs they'd be OK, but maybe while I've got them out for an airbox change, I'll give the jets a bit of a blow through.

There's usually some fuel left in places where gravity won't help, this can turn into a hard 'varnish' coating.

[Geoff W]

I read in an old Classic Bike magazine a few years back, it had a recipe for reviving old carb rubbers, and other rubbers that have hardened.
Basically boil up a solution of 1 part Oil of Wintergreen to 40 parts water and drop the rubbers in for half an hour, making sure that they do not touch the bottom of the pan( put in a sieve or similar.) Supposed to return them to shiny and flexible. HOWEVER it says do this outside and even then you will still need a gas mask. It probably repels Scottish Midges as well.

[GavD]

Think I'm all sorted now guys, new airbox and rubbers turned up, fitted em and slung in some fresh fuel.

Bike started Ok but revs quickly shot up to about 3000 and just sat there. Killed the bike, spent about 20 mins scratching head then found I'd not got the throttle cable back in properly and it was partially open. The crispness is back in the throttle when sat on the drive warming up, and the revs drop nicely now. Amazing how ladies of a certain age appreciate having a bit of money spent on them!!!

Hopefully first ride of the season this sunday to prove all is good.

P.S I've got a sneaky suspicion that Richard the speed triple fan has an XRT on the way. He took one out when his S3 was in and loved it. Looks like last years meet in wales has converted both him and Mo!!

[nickjtc]

Amazing how ladies of a certain age appreciate having a bit of money spent on them!!!

If it's got t!ts or tyres, it is ALWAYS going to cost you money...

[threepot]

Think I'm all sorted now guys, new airbox and rubbers turned up, fitted em and slung in some fresh fuel.

Bike started Ok but revs quickly shot up to about 3000 and just sat there. Killed the bike, spent about 20 mins scratching head then found I'd not got the throttle cable back in properly and it was partially open. The crispness is back in the throttle when sat on the drive warming up, and the revs drop nicely now. Amazing how ladies of a certain age appreciate having a bit of money spent on them!!!

Hopefully first ride of the season this sunday to prove all is good.

P.S I've got a sneaky suspicion that Richard the speed triple fan has an XRT on the way. He took one out when his S3 was in and loved it. Looks like last years meet in wales has converted both him and Mo!!

I liked the XRX I rode recently. I think the XRT will be better on tarmac though,with the smaller front wheel?

[Sin_Tiger]

Can't comment on the new models but I felt the 21" was better handling and a little more nimble, I know it shouldn't be in theory.

[nickjtc]

Can't comment on the new models but I felt the 21" was better handling and a little more nimble, I know it shouldn't be in theory.

Skinnier tyre? Less total rotating mass than the smaller wheel??