carb issue

[xswisconsin]

Hello,
I have cleaned my carbs often lately due to rusty tank that i have now fixed. The issue that I am having is this: after running for about 10 minutes the engine tends to rev high. I check the throttle to make sure it isn't sticking and that is not the issue. any thoughts?

 

[CDNTX650]

Number of things. Air leaks at carb boots, sticking atu if you have a non tci model. Do a search.

 

[xswisconsin]

I have cone air cleaners. what is an atu

 

[CDNTX650]

Look in the tech section, or search google. There has been hundreds of threads on this.

 

[5twins]

Research air filters as well. Sounds like you have the el cheapo bad ones. Tuning will be very difficult using them.

 

[fredintoon]

Hello,
I have cleaned my carbs often lately due to rusty tank that i have now fixed. The issue that I am having is this: after running for about 10 minutes the engine tends to rev high. I check the throttle to make sure it isn't sticking and that is not the issue. any thoughts?

Hi wisconsin,
5 posts and not much forrader, eh?
Details, dammit, details.
WTF bike/year/model/modifications has the problem?
Build that data into your signature line.
And did it always do this or only since you fixed it?

 

[xswisconsin]

81 xs 650. I don't recall this happening prior to rebuild, but haven't ran the bike for about 10 years prior to the rebuild. Motor was left alone, exhaust pipes are stock with shorty mufflers on them. Carbs were rebuilt with xs 650 kit ( basically needle valve and gasket) from Mikes. pod filters are mikes. I did not change the jetting. I am just wondering what other than giving it gas with the throttle will cause the carbs to allow more fuel and air into the motor seeing as how the butterfly valves are mechanically controlled with the throttle.

 

[fredintoon]

Yeah, but the slides and needles are controlled by the carb diaphragms.
How bad is it?
If it goes from ~900 rpm idle when cold to ~1,200 rpm idle when hot, that's usual.
If it just climbs and climbs, there's a problem.
I'd say clean the carbs yet again and pay particular attention to the diaphragms, both that they are not perforated and that they are seated correctly.
And that's the MikesXS pleated oval pods that say XS on them?
We have 8 of those (on 2 XS650s and an XS11) that work just fine.

 

[barelycompetent]

If you used the needles in the mikes kit it could be those. Change them back to stock. It could be air leaks at the boots, or it could be a lean condition as well that only shows up when warmed up. If you blip the throttle do the rpm's come back down? \

 

[xswisconsin]

thanks, and yes it is the xs pleated oval pods. I will check the diaphragms again. It does tend to keep climbing in RPM. after a bit or sometimes after i gas the throttle it will go back down.

 

[xswisconsin]

sometimes it comes back down sometimes it doesn't

 

[barelycompetent]

Put the stock needles back in, it sounds like a lean condition to me. What size jets are you running? Your carbs should be bs34's on an 81. You have to rejet for pods, usually one size bigger on the pilot jets, and two on the mains, should get you in the ballpark. You also need to adjust your mix screws out as well, usually 3 turns to start.

 

[CDNTX650]

45 pilot and 140 mains should get you in the ballpark. I had to drop my needles by sanding about a half a step off of the plastic donuts that hold the needles. Could be an airleak at the carb holders too. Inconsistant idle and revs climbing can be a carb sync issue too.

 

[XSLeo]

www.amckayltd.com/carbguide/pdf Have you read it?
Leo

 

[joebgd]

once they warm up nice and good the idle is at a higher level, in my experience.

 

[scabber]

Three turns out mixture might screw lean idle circuit when it heats up. If still problem try a 45 pilot jet. the mains don't change.

 

[gggGary]

Have you synched the carbs?