RXS 2 stoke rebuild on non runner, high idle

skeverd · Borekit Bruiser Joined: 22 Nov 2009 Karma :

I completed a rebuild on my Yamaha RXS which i bought as a non runner. I started the bike up and its revving very high to the point where i felt it was necessary to switch of the ignition after less than a second or so.

The rebuild included a carb clean. Also the bore was increased to 1.00 oversize.

I put the engine in, and connected everything up. I started it via encouragement using a small amount of fuel in spark plug hole. Pilot screw is set to 2.5 turns out.

The throttle is adjusted so there is maximum slack on the cable (the cable also fails to return?)

I wondered if anyone has come across anything similar? if so what could be done to rectify the issues?

Thanks. shamen.

..... · Quote Me Happy Joined: 15 Jan 2005 Karma :

Air leak on the carb side of the engine? Check the carb is seated in the rubber boots correctly and that they aren't cracked. Don't over tighten the clips around them either.

skeverd · Borekit Bruiser Joined: 22 Nov 2009 Karma :

I did have trouble getting the carb in place with the air filter, mainly bc it was dark during re-assembly. i shall check tomorrow and post back asap. any idea about the non returning throttle issue?

chris-red · Have you considered a TDM? Joined: 21 Sep 2005 Karma :

skeverd · Borekit Bruiser Joined: 22 Nov 2009 Karma :

'Just' a pod filter? i thought these hip nd withit people add those on? Laughing

nah, just the standard airbox, i want to keep it original, i want it to be a reliable bike - i figured keeping it as close to standard would help me with that?

skeverd · Borekit Bruiser Joined: 22 Nov 2009 Karma :

well its running =D only now it wont idle - and revs take so long to go down also Sad

on the other hand twist grip returns Very Happy

any idea on the 2 problems stated?

Carvel · World Chat Champion Joined: 01 Jun 2010 Karma :

skeverd · Borekit Bruiser Joined: 22 Nov 2009 Karma :

ive set the pilot screw to 2 and a half turns out as mentioned above... with this the bike still wont idle regardless of the idle screw position.

it seems like its going to die, so i adjust the tickover and then it chooses to rev up high and take ages to then return to almost dying again. if i leave it it does die...

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

This is going to sound a bit crazy but being that the throttle cable doesn't return as well as the high idle...

... Is the throttle slide in the right way around? I know its easily done as I did it meself when I rebuilt my RD350...
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Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

SpannerMonkey · World Chat Champion Joined: 26 Aug 2010 Karma :

skeverd · Borekit Bruiser Joined: 22 Nov 2009 Karma :

haha, yea, this infact was the problem, though i already rectified it Embarassed

but yea, now i just have the inability to idle and the revs not settling... Crying or Very sad

SpannerMonkey · World Chat Champion Joined: 26 Aug 2010 Karma :

skeverd · Borekit Bruiser Joined: 22 Nov 2009 Karma :

no i havnt changed the plug, but it seems fine atm.

Another problem, the clutch seems to be either enguaged or not engaged - theres no in-between! this seems to be a problem with the whole starting thing... Crying or Very sad

Not sure if its normal, but when i kick the engine over without the ignition on, i can feel air coming out of some sort of nipple on the carb? right hand side...

cb1rocket · World Chat Champion Joined: 30 Jan 2010 Karma :

Have you adjusted the tickover/idle screw - its not the same as the pilot screw in case you wondered... hence the high idle

27cows · World Chat Champion Joined: 01 Nov 2009 Karma :

Idle screw should be around 1 1/4 turns out. 2 1/2 is way too much.

Non-returning throttle could be caused by the twist grip being pushed too far onto the bar, or because the inner plastic is damaged or chafing at the end of the bar, or because the cable isn't routed correctly. Small possibility of the throttle slide being round the wrong way but that normally results in hysterical high revs as soon the motor fires up.

You shouldn't have air coming out of the carb when turning over the motor, I don't think Shocked

Have you got the various pipes on the right places?

Making an RXS run anything but nicely actually takes a bit of doing in my experience, so look for something pretty obvious Wink

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The RXS100: vehicle of choice for Chuck Norris

skeverd · Borekit Bruiser Joined: 22 Nov 2009 Karma :

Carvel · World Chat Champion Joined: 01 Jun 2010 Karma :

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

Stuck float could be a contributing factor. Giving the carb a good solid tap with the back of a screwdriver generally gets them to settle down.

When I have had trouble with the revs dieing down very slowly it has been down to a clogged up mixture circuit - so the pilot screw isn't doing anything, and the idle screw is wound in a lot to compensate.

The solution there is to take the carb out, remove the mixture needle and spring, blast plenty of carb cleaner into its hole (using a long straw on the nozzle) and reassemble. Often caused by rusty water in the tank getting into the carb and blocking this hole, so fit an inline fuel filter if you don't already have one.

skeverd · Borekit Bruiser Joined: 22 Nov 2009 Karma :

Yea, thats a good point, however currently pre mixing the bike for first tankful, just for easier access whilst tinkering with it.

Urm, there is rust in the tank, however i also did clean the carb beforehand with plenty of carb cleaner. I suppose i should do this again at some point, and put a filter in also.

the pilot screw does change the idle though... but its worth a shot. als, this air escaping from the nipple on the carb is concerning me now.

thinking back i remember looking down the reed valve and noticing one of the fins was bent ever-so slightly to the point where there was a small gap? is this a big problem? is there a way i could straighten it?

27cows · World Chat Champion Joined: 01 Nov 2009 Karma :

So you're premixing the bike and presumably there's no pipe on the oil intake stub. Could well be the problem.

Unlikely a slightly bent reed petal would cause this problem. I always use the Hy Tech fibre ones myself, though.
____________________
The RXS100: vehicle of choice for Chuck Norris

skeverd · Borekit Bruiser Joined: 22 Nov 2009 Karma :

Which nipple does the oil feed pipe go to n the carb? is it the one nearest the oil pump on the right hand side just above the float chamber?

i could see why this may be a problem - does the engine have a vacuum effect on the oil feed pipe as well as the pump delivering oil? as I suppose this would mean its effectively an air leak?

27cows · World Chat Champion Joined: 01 Nov 2009 Karma :

skeverd · Borekit Bruiser Joined: 22 Nov 2009 Karma :

Then your a genious! It seems the most logical problem, thanks! Very Happy

I shall sort it tomorrow and report if its solved the situation.

Another note, the oil pump is set so the end of the cable is in line with the little pin thing on the pump body right?

27cows · World Chat Champion Joined: 01 Nov 2009 Karma :

skeverd · Borekit Bruiser Joined: 22 Nov 2009 Karma :

So ive found that by placing my finger over the oil inlet on the carb does enable the engine to idle finally Surprised

Thanks again Very Happy

However the rpm still take a rather long time to die back down?

and the clutch is still failing to have any sort of slip in it. (by slip i mean it cannot partially engage, its either not engaging - or fully engaging) no matter how slow you release its it still effectively dumping it. Confused