97 Honda CR250 Surging at Idle

[HAYSHAKER170]

I have a 1997 Honda CR250 stock except FMF Fatty exhaust. When I am riding and then come to a complete stop with the clutch pulled in, the idle surges up and down for 20-30 seconds B4 it becomes a nice idle. I was thinking I would clean the carb and take note of the jetting sizes and do a general inspection of everything. Anything come to mind. Thanks in advance! :bang:

 

[ktal74]

My 97 CR250 did this too. I cleaned the carb, changed jetting but nothing seemed to fix it.

Then I started using half 110 octane and half 91 octane in my premix. Cured the surging problem for me immediately. The surge would make the bike lurch in the slow corners, which was very dangerous. No problems with this now.

I hope that helps.

 

[2 strokes for life]

It sounds like you have a slight bit much compresion. Thats why useing 110 octane fixed his problem. But my question would be if it did not do it befor why now. It also could be a vacume seal leak. I would replace the head and base gaskets and see ehat that dose.

 

[john stu]

lean jetting!!!!

 

[jason33]

check the vent tubes- and look for air leaks at the boot- loose main jet
ect...

 

[UTDesertman]

Doesn't the carb on the 97 & 98 CR250 also use an electronic idle switch or something like that?

 

[dirt bike dave]

Doesn't the carb on the 97 & 98 CR250 also use an electronic idle switch or something like that?

The powerjet carb on those bikes only goes into effect at high rpm. Basically, a solenoid triggers at a certain rpm and actually reduces the fuel. If the solenoid stops working, you will lose a little high rpm power, but it will not effect anything else.

It is easy to check the operation by removing the solenoid from the carb and hooking the wires to a 12v source. If it trips the solenoid when you give it 12v, it is probably working fine on the bike.

 

[jason33]

some do not all of them though-
they should have skipped that and went straight to fuel injected!
or direct injection-- 4 strokers as well

 

[Broken Spoke]

Did you recently pull the stator off? It could be a timing issue in addition to the lean jetting.

 

[HAYSHAKER170]

No I didn't pull the stator cover off recently. I am not the original owner and it has done this surging to some degree since I bought it 2 years ago. It seems to do it less the warmer the air is so maybe it is lean jetting. Recent ride air temp was about 45-55 F. In the warmer days of summer it is much less or non-existent. But it runs great when I am on the gas, so it's more annoying than anything. But too lean would not be good.
I know 2 strokes are not meant to idle, but I like mine to be able to idle for 5-10 seconds with out stalling. I am a woods rider, not racing. What's a good guideline for idle time?

 

[jason33]

all bikes should be able to idle-
if they load up there running rich- they should run the same from idle to wide open
after warm up of course-

 

[skiboyracing]

My 99 does this same thing, it will never stall out, just surges at idle for a bit. Mine also does it more when colder. I actually leaned out my main from stock a little bit but it didn't make much difference. It's annoying for sure. Maybe I need to fatten the idle air jet?

I was thinking it may be my boysen reeds not sealing well? Not sure if that would do it. I do have a 265 kit in it so maybe the compression has increased on mine. Is yours a stock bore?

 

[dirt bike dave]

I am not the original owner and it has done this surging to some degree since I bought it 2 years ago. It seems to do it less the warmer the air is so maybe it is lean jetting.

I know 2 strokes are not meant to idle, but I like mine to be able to idle for 5-10 seconds with out stalling. I am a woods rider, not racing. What's a good guideline for idle time?

If it is a little lean during cooler weather, you can turn in the airscrew to richen it up. 1/2 turn in should make a noticeable difference. It might soften the 'hit' a little bit. Could be good or bad depending on your preference.

The idle on the '97-98 CR250 is adjusted by rotating the choke knob. Sorry, I can't remember if it is counter-clockwise or clockwise to speed it up. Most racers set the bike up for the best throttle response and sometimes it will not idle. Not a problem for MX, but if you want it to idle for trail riding you should be able to get it there with some carb adjustments, at the expense of low rpm throttle response.

 

[HAYSHAKER170]

I just want to thank everyone who replied. This site has really been a great help to me on several occasions. Great site and great people. Keep up the good work. Now let's go ride!!!

 

[skipn8r]

A surging idle with nominally correct jetting could signal a vacuum leak. Could be a worn left side crank seal which is a fairly quick repair. Given that the bike is a '97 and you're not the original owner, it's very possible. After you chase down the easier stuff, you might want to pressure test the engine.

 

[RACER557]

go up one or two pilot jet sizes for cold weather. then reset air screw at manu settings. with proper jetting the bike should idle fine. like skipn8r said start with the simple stuff first. good luck!!

 

[HAYSHAKER170]

Thanks for the replies. This weekend I am going to remove the carb, clean the carb, make note of the jet sizes, check the reed valves for any cracks then put it all back together and take it for a test spin. If it still does it then I will richen the pilot jet 1-2 steps. If that doesn't help then get the vacuum leak test. Hopefully, the jetting works. Thanks again everyone!