Bike idling funny

[RoyMember]

My bike (09 300 2T) has an issue at idle. When I pull up it will surge up and down the revs for a while before finally dropping back to normal idle revs. It has only just started doing this after I full off all the subframe to replace part of the air box plastics on the weekend, so I’m guessing some shit got in there during that process. There was also a bit of a brown stain on the top of the throttle slide that I could see so I wiped that off too. It looked a bit like oil residue. The bike will still idle and does not stop running just either idles a bit high or surges for a while. Once it finally drops back to normal idle revs it seems to stay there.

Is it hard to pull the carby apart and clean. ie. is there stuff in there that has a certain setting that can be changed by me stuffing with it accidently. Or is it just a matter of pulling things apart and putting back the same way.

I pulled the carby apart on my peewee 80 when I was a kid so have a bit of an idea of what to expect and it still ran when I put it back together, but I wasn’t afraid of consequences back then and I wasn’t footing the bills either.

PS. I have tried the chinese tune up technique already and it didn’t seem to help.

[DeanMember]

Roy sounds like you have some water and or crap in the Carb. Easy to fix and do.

1. Remove the carb cap and slide/needle
2.undo the bottom drain cap carefully (try not to spill the contents as you want to check for water/crud
3. loosen off both retaining clips that hold carb to reed block and air filter boot
4.pull airboot to the rear and try and wedge behinf a fram downtube to hold in place.
5.remove carb to the rear
6. place carb in ice cream container or similar and give all externals a really good clean with petrol and a tooth brush
7. place a nice clean paper towel on work area
8. turn carb upside down and remove the 4 phillips head screws (ensure you use right size screw driver as they strip easily) also not where the the screwws come from as they may have hose retaining clips on them
9. remove sliding pin on floats and needle seat. do not touch or adjust the little tang as this will adjust your float height!
10. remove all of your jets Im tipping your pilot jet will be the culprit (usually is)Hold the jet up to a bright light and check for blockage
11. Blow all orifices through with compressed air or a can of Carb cleaner or WD40 etc
12. clean all interiors of Carb
13. reasssemble in the reverse order
14. Maybe look at putting an inline fuel filter on.

Also you should check for air leaks

hope this helps

Ollie

[Mick DMember]

+1 on the airleak.

[RoyMember]

Thanks for the tips. I’m guessing by air leaks you mean holes in the air box boot or can these happen in the carby and/or the reed block as well.

I was going to take the drain plug out of the carby and check for water as well but haven’t had a chance yet.

Any idea what the brown stain on the back of the throttle slide might be. It was right up the top of the slide as you look in from the back where the air boot connects. I’m guessing this means the whole thing needs a good clean anyway.

Have been thinking about putting in an inline filter for a while now as I’m always filling from jerry cans. Any good brands.

[DeanMember]

Check the seal where the cap screws down onto the body of the carb. If it doesnt seal properly you will have dramas. Also where the boot joins the airbox is another likely place.
yes you can get an air leak at any of the mentioned places.

to check: have engine running spray WD40 at the above areas 1 area at a time and listen for a change in the engine revs

Ollie

[RoyMember]

Now that it is a necessity to clean my carby I have been thinking and have a couple of other questions before I commence.

With the mixture/air/idle screws or whatever they are called is there a need for me to take them out as part of the cleaning process. If so, in order to make sure I put them back right do I just measure the number of turns from fully screwed in to the current position. Should I do that anyway just to know where things are set.

[GregMember]

Bundyroy wrote:

Quote:

Now that it is a necessity to clean my carby I have been thinking and have a couple of other questions before I commence.

With the mixture/air/idle screws or whatever they are called is there a need for me to take them out as part of the cleaning process. If so, in order to make sure I put them back right do I just measure the number of turns from fully screwed in to the current position. Should I do that anyway just to know where things are set.

Yes mate count the turns and write it down, perfect Wash it all I use petrol and blow everything out with a blow gun on the compressor.

Take your time, clean is your friend

TB

[RoyMember]

Thanks TB,

I did a bit of an internet search the other day as well. Found a site and the bloke said that he reckons blowing out crap hardly ever works and he reckons the go was putting it in boiling water. Have you ever heard of this. The site I was looking at appeared to be a bloke who repairs old bikes so I’m guessing he had to deal with a lot of long term hard set crap from years of abuse as apposed to my carby which ahs been in constant use for only a couple of years. Just interested in hearing others thoughts on the boiling thing.

[Bruce CurtisMember]

Old bikes= old materials and that beaut green crap from fuel/alloys interacting poorly.

I wouldn’t heat a late model Carby too much for fear of warpage or destroying a plastic insert somewhere.

Blowing is good, if it can’t be blown it’s in need of a little chemical help.

[Jeffrey SmithMember]

Water only boils at 100°C, at that temp it wouldn’t cause any distortion of the metal but I wouldn’t know about any possible plastics.

[RoyMember]

Finally bit the bullet on the weekend and got stuck into the carby. All came apart fine. Pulled the bowl off. No dirt or water there, not that I was expecting much after the royal flushing it had when I pulled the drain plug out the weekend before with the fuel tap still on.

I then unscrewed everything thst I could on the top half of the carby. Dosed everything with a healthy spray of carby cleaner and blew out all the internals. The only place I noticed where there was some blockage was the bit right in the middle. It was a brass bit that was a 6mm nut on the end with a hole up the middle (the rest undid with a screwdriver). Held it up to the light, no light (wasn’t sure if there was meant to be at this stage). Blew on it and then all of a sudden there was now a reasonable size hole (well compared to the size of some of the others).

I thought there was more than one needle in a carby. The only needle I found was under the float to stop the fuel coming in from the tank. What are the jets? And people talk about the clip position. What is this, I didn’t see any clips.

I hope I did it right. I put everything back as it was and the bike seems to run better. I’m just a bit worried as I din’t seem to find all the bits I hear about that I didn’t pull it down far enough and there may still be shit in there.

[Mick DMember]

Bundy.

The 6mm nut thingy with the hole in it,is actually your main Jet and the smaller one next to it, that screws out with a screwdriver, is your idle or pilot jet. The needle that hangs down from your slide goes into your main jet.

That is the needle people refer to.

That needle has 4-5 slots at the top of it,that are only visible if you pull the needle from the carby slide.Those slots are what the clip goes in and that clip determines how far your needle will go down into the pilot jet.

I have tried to put this in layperson speak. If someone can explain it better go right ahead.

BTW Bundy,is it idling any better now you have cleaned the carbie??

[RoyMember]

Thanks Mick. I do understand what you mean. Thought about undoing the needle on the slide but thought I was only creating work for myself and let sleeping dogs lie. I did pull out the idle jet. It has a little setup on the end that looks like a filter with 8 litle pin holes. I did spend a fair bit of time cleaning and blowing it out. Bike seems to idle fine now but I did only take it for a 5 minute ride so I will need to do a decent ride before I am convinced I have rid myself of the problem.

[AlexMember]

Bundyroy wrote:

Quote:

…Thought about undoing the needle on the slide but thought I was only creating work for myself and let sleeping dogs lie.

Let it be said that lubricant from the throttle cable or water+grit from washing the bike can be real good at gravity feeding down the cable into that needle/slide area.

Up to you, if everything is good then leave it. Otherwise tilt the carb a bit and slide out the throttle slide. Undo the cap/nut you see to release the needle. You’ll notice the spring keeping some tension. Make sure parts don’t go flying everywhere. I bet you there will be grit sitting there somewhere. Take note how the plastic seats in there are placed as it is very easy to assemble incorrectly and cause yourself headaches. Throttle must snap shut. No spring noise or funny sounds from the carb end when winding the throttle on and off.

[RoyMember]

Yeah the spring was why I left it alone. After fixing up my starter motor I hate spring loaded stuff. My gumby fingers are not designed for dainty work.

Two last questions regarding the carby.

1. When I put the carby back in I thought “what angle”. I assume it goes in a vertical position when bike is vertical. That’s where it is at the moment anyway. I look at the thing every day and for the life of me I wasn’t sure at the time.

2. The idle jet (the long thin one that steps down to the filterish looking end)that is in the bottom of the tube beside the main jet. Should you be able to see light through that. I could blow through it reasonably easily but could see no light and when I put a bit of thin necklace wire up there it would not go through. I did not try and force it as I thought if it was only dirt blocking the way then it should give easily.

One last piece of advice for people planning on doing this. Have a look at the schematic in you bike parts catalogue. I just did and I must say things are a lot clearer now.

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