engine idles high only when warm

gordon2418 · 09-04-2014, 10:08 AM

I just bought what I believe to be a jetmoto 250cc. It starts and idles perfect then I take it out for a ride. Upon returning from ride and trying to let idle it seems to idle very high. I would know what to do if it were a car but and am brand new to atv's. I can't even seem to find a service manual to know what to even look for.

Any help greatly appreciated.

andrew

Sunl1979 · 09-04-2014, 05:08 PM

You should be adjusting you carb will its warm so you can control the rpms while it in operating mode. So try and turn down the idle screw while it is warm, and see if it till fires up ok when it is cold also.

Weldangrind · 09-04-2014, 11:51 PM

Welcome, Gordon! Where in Ontario are you?

When you rev up the motor and release the throttle, does it settle down right away, or take a few seconds?

gordon2418 · 09-05-2014, 07:48 AM

Quote:

Originally Posted by Sunl1979

You should be adjusting you carb will its warm so you can control the rpms while it in operating mode. So try and turn down the idle screw while it is warm, and see if it till fires up ok when it is cold also.

If you are referring to the little silver screw on the side of the carb I will try that I did not know what was the idle screw as I don't have a manual of any kind for this bike.

gordon2418 · 09-05-2014, 07:49 AM

Quote:

Originally Posted by Weldangrind

Welcome, Gordon! Where in Ontario are you?

When you rev up the motor and release the throttle, does it settle down right away, or take a few seconds?

I am in a little town called Milford. It is south of Picton. Yes it does settle right back down immediately but just not as low as it should be.

humanbeing · 09-05-2014, 08:14 AM

Quote:

Originally Posted by gordon2418

...did not know what was the idle screw ...

Keihin clone: http://www.walbro.com/media/22805/pz-tune.pdf
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http://www.motorfans.com.cn/bbs/view...authorid=75082

gordon2418 · 09-05-2014, 08:35 AM

Quote:

Originally Posted by humanbeing

Keihin clone: http://www.walbro.com/media/22805/pz-tune.pdf
---

http://www.motorfans.com.cn/bbs/view...authorid=75082

Thank You humanbeing that was exactly what I was looking for. Am new to atv's and don't where to find the info but apparently this forum was a good place to start.

gordon2418 · 09-05-2014, 09:04 AM

Ok I have done as sunl1979 said and adjusted the idle now it does not idle really high when warm but seems to want to stall when cold I guess it is just a matter of finding a happy medium now.

humanbeing · 09-05-2014, 09:21 AM

http://www.microsofttranslator.com/b...%3D15274249845
Digital tacho is very useful tool tuning "chinese" & old bike : CG clone is 1400 +/- 100 rpm

bogieboy · 09-05-2014, 11:18 AM

Quote:

Originally Posted by gordon2418

Ok I have done as sunl1979 said and adjusted the idle now it does not idle really high when warm but seems to want to stall when cold I guess it is just a matter of finding a happy medium now.

thats common... my cg200 based dirtbike is the same way... however if the choke is partly on, it will idle ok for me... just takes about 5 min to warm up...

Weldangrind · 09-05-2014, 11:23 AM

The idle was set high to crutch the small slow jet.

I've found that the slow jets are too small, especially when the weather gets a little colder. Slow jets are difficult to find for that carb, but Mikuni jets are found at your local Yamaha dealer, in addition to eBay.

A 30mm Mikuni is cheap and worthwhile, so you can begin tuning. $42.28 Canadian to your door: http://www.ebay.ca/itm/VM26-30MM-MIK...1d2238&vxp=mtr

Weldangrind · 09-05-2014, 11:30 AM

Quote:

Originally Posted by gordon2418

I am in a little town called Milford. It is south of Picton.

I bet it's nice to be that close to the lake. I've never been to Milford, but I've travelled through Cobourg and Kingston, so not too far off.

gordon2418 · 09-06-2014, 01:37 PM

Quote:

Originally Posted by Weldangrind

I bet it's nice to be that close to the lake. I've never been to Milford, but I've travelled through Cobourg and Kingston, so not too far off.

I love being close to the lake and the fishing is plentiful as well. I bet living out by the Rocky Mountains is awesome as well. I made another minor adjustment to the idle screw seems to work much better but will look into that jet as well. Just did an oil change on it as well and used Rotella T 15W 40 does that ok for it.

Weldangrind · 09-06-2014, 02:32 PM

15W40 is all I ever use. I'm happy with Rotella, Delo or Delvac; whatever is on sale.

gordon2418 · 09-09-2014, 03:05 PM

This would seem to be fixed now and have that Mikuni Carb on order as well just because i want a better setup and adjustability.

09-04-2014, 10:08 AM	#1
gordon2418 Join Date: Aug 2014 Location: Milford, Ontario, Canada Posts: 18	engine idles high only when warm I just bought what I believe to be a jetmoto 250cc. It starts and idles perfect then I take it out for a ride. Upon returning from ride and trying to let idle it seems to idle very high. I would know what to do if it were a car but and am brand new to atv's. I can't even seem to find a service manual to know what to even look for. Any help greatly appreciated. andrew __________________ They all pretty much come from china anyway.
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09-04-2014, 11:51 PM	#3
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Welcome, Gordon! Where in Ontario are you? When you rev up the motor and release the throttle, does it settle down right away, or take a few seconds? __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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09-05-2014, 09:04 AM	#8
gordon2418 Join Date: Aug 2014 Location: Milford, Ontario, Canada Posts: 18	Ok I have done as sunl1979 said and adjusted the idle now it does not idle really high when warm but seems to want to stall when cold I guess it is just a matter of finding a happy medium now. __________________ They all pretty much come from china anyway.
	0

09-05-2014, 09:21 AM	#9
humanbeing Join Date: Mar 2008 Posts: 2,436	http://www.microsofttranslator.com/b...%3D15274249845 Digital tacho is very useful tool tuning "chinese" & old bike : CG clone is 1400 +/- 100 rpm __________________
	0

09-05-2014, 11:23 AM	#11
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	The idle was set high to crutch the small slow jet. I've found that the slow jets are too small, especially when the weather gets a little colder. Slow jets are difficult to find for that carb, but Mikuni jets are found at your local Yamaha dealer, in addition to eBay. A 30mm Mikuni is cheap and worthwhile, so you can begin tuning. $42.28 Canadian to your door: http://www.ebay.ca/itm/VM26-30MM-MIK...1d2238&vxp=mtr __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

09-04-2014, 05:08 PM	#2
Sunl1979 Join Date: Sep 2014 Posts: 4	You should be adjusting you carb will its warm so you can control the rpms while it in operating mode. So try and turn down the idle screw while it is warm, and see if it till fires up ok when it is cold also.
	0

09-06-2014, 02:32 PM	#14
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	15W40 is all I ever use. I'm happy with Rotella, Delo or Delvac; whatever is on sale. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

09-09-2014, 03:05 PM	#15
gordon2418 Join Date: Aug 2014 Location: Milford, Ontario, Canada Posts: 18	This would seem to be fixed now and have that Mikuni Carb on order as well just because i want a better setup and adjustability. __________________ They all pretty much come from china anyway.
	0