Runaway idle

Steve150xc

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Apr 20, 2015
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Haven't found anything regarding what I call "Runaway idle". I just bought a 2006 blaster which I bought from the original owner, who says it's all stock. He said he recently had the carb rebuilt. Well I found the pilot airscrew turned all the way in, so I have been trying to re-adjust it but I'm still getting these super fast idle speeds more like wide open throttle. Some of you have mentioned on here about the idle speed adjuster screw being under the rubber flap, but I haven't had any luck with it???

Update: I just removed the t.o.r.s cover and found that the adjustment screw had been turned too much, and therefore was dis-connected from the black plastic piece with the spring on it, so I reattached it. -Further updates can be found down the page-
 
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A run away idle like your saying is usually an airleak!

On the top of the Tors brick on the carb, there should be about a nickel sized knob that has a flat head screwdriver slot in it. Turn it clock wise to increase the idle, CCW to lower it.
 
Put it back together and started it. It is running good, I turned pilot screw about 1&1/2 turns out, just like it should be. Made some turns on the idle screw.

Update: Just went out and put a little more free play in thumb throttle because there wasn't much after I put everything back together. Then I started it and my tachometer was showing around 1450. It seems slightly boggy off of idle but I will ride and fine tune a little more as I go. This tors thing makes adjustment a little more complicated than machines without it...none of my other machines ever had it or even something like it. The only mods this machine has as far as I can see is the EHS Racing airbox lid screen that I installed. and the front radial holeshot SR's I put on.

@dirtysquared: I think in my case the run away idle was due to the dis-connection of the cable?? inside the tors box. Doesn't mean there can't be an air leak but, so far it sounds good/idles good/revs good.
 
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Although it seems to be running fine as it is, it is imperative that you make sure that you leak test the motor. A small leak can and will fry your piston and you will be doing a top end rebuild. Please do not run the bike until you are sure its leak free. Preventative maintenance now will ensure a long time of riding worry free.
 
Steve, if the Tors block on the top is troublesome to you, a good option I'd a tors delete kit. It gives you a plain carb cap, and an idle screw that goes into the side of the carb.

If your handy and not afraid to drill AMD tap your carb ,its a good upgrade instead of the clumsy brick on top of the carb.

You can find that kit on eBay all the time. Vito's and motion pro are both good.
 
n't
Although it seems to be running fine as it is, it is imperative that you make sure that you leak test the motor. A small leak can and will fry your piston and you will be doing a top end rebuild. Please do not run the bike until you are sure its leak free. Preventative maintenance now will ensure a long time of riding worry free.
I know it could fry a piston but I am not seeing indications of an air leak at this point, are you?

My upper half seems air tight, I did a compression test the other day and I got 110. I'm good with that on a 9 year old machine. I have to go with the evidence here, when I removed the tors cover today I found the screw dis-connected from the black piece with the spring on it, I think that was the cause of todays runaway idle. Also I see that (probably due to tors) the idle speed seems to be effected by the slightest adjustment of play at the thumb throttle. I had installed a bar riser kit but the throttle cable was snug with the risers in place. So I removed the riser kit to eliminate it as a possible cause. May try the riser kit again later.

Would a leaking case or some other leak, give a symptom???

On an auto engine, if you did a compression test and one or more cylinders was low, you might do a leak down test to help clarify the source of low compression i.e. intake valves, exhaust valves, rings, also you could do a wet compression test to see if the low cylinder comes up substantially.

But I'm not seeing a problem that is leading me to believe that my blaster is sucking air.
The carb still dribbles if I leave the fuel on...I may need to bend the tang on the float.
 
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The bogging could also be caused by a lean condition. Did you up your jetting when you put the new lid on? If not you need to, maybe as much as 2 sizes. What are your temps and elevation? And leaktesting is just part of 2 stroke maintenance, should be done twice a year
 
I know it could fry a piston but I am not seeing indications of an air leak at this point, are you?

If you don't have a hanging idle, probably not. But, if you removed stock lid/snorkle you will have to increase the main jet size because it is getting more air. If lid was already removed you should check to see if main jet was increased or not. Stock is 220 or 230 depending on year.

As to the bog, try adjusting the air screw 1/16-1/8 turn.
 
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When I blew my last motor up, it was running perfect! No problems what so ever. I bought a tester from awk and tested that engine before teardown. Was losing 1 psi/min. Found leaks at the reed cage and where the cases meet. My point is just because its running fine doesnt mean there isnt a problem that needs to be addressed.

I know it could fry a piston

If your fine with possibly spending a couple hundo rebuilding when you could have spent $30 then i cant stop you.
Now I know when you read through the forums almost everyone suggests doing a leak test as a solution to a problem, this is for good reason.
 
The bogging could also be caused by a lean condition. Did you up your jetting when you put the new lid on? If not you need to, maybe as much as 2 sizes. What are your temps and elevation? And leaktesting is just part of 2 stroke maintenance, should be done twice a year

Jetting 230. When I bought this machine two weeks ago it was sluggish, it was like a 200 four-stroke lol, not like a 200 two stroke should be, of course I'm probably comparing it to my two-stroke KTM 150xc. But I removed the air lid and drove it around my house and it was night and day difference, very strong and responsive so I ordered an open box lid with a screen on it, which I received the other day and has been installed since.

However, I learned today that the pilot screw was closed....

I'm near Detroit, MI. 72 degrees today.

But can u clarify why I need to re-jet?

Simply making air more plentiful to the air box and filter (by, in this case, using a screened lid) does NOT FORCE FEED more air into the carb. The carb will suck in what it is able to suck in, through the air filter, based on throttle position & carb settings & air conditions, therefore, if you are suggesting that a higher volume jet is mandatory you are NOT entirely accurate. You could in fact, be too rich if you were to up your jets in this case.
 
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did not read your post anything past 110 psi
but it is lacking a tiny bit in compression. or it is the gauge?
it should be at 120 psi or above:)
i have seen terrible top ends on a blasters/piston/cylinder bores with 120 psi :)

it is more important how a engine is tuned/more then it's cubic centimeter displacement.
example a yz125 would smoke a blaster 200 engine/transmission:eek:
 
sometimes pics of your
quad/carb setup's can determine problems issues:D
stock blaster is 17hp,your ktm 150 i assume is much higher:)
but the blaster is tons of fun regardless the hp output:D
quads will always be slower then bike's cuz of weight differences ect..
 
did not read your post anything past 110 psi
but it is lacking a tiny bit in compression. or it is the gauge?
it should be at 120 psi or above:)
i have seen terrible top ends on a blasters/piston/cylinder bores with 120 psi :)

it is more important how a engine is tuned/more then it's cubic centimeter displacement.
example a yz125 would smoke a blaster 200 engine/transmission:eek:
did not read your post anything past 110 psi
but it is lacking a tiny bit in compression. or it is the gauge?
it should be at 120 psi or above:)
i have seen terrible top ends on a blasters/piston/cylinder bores with 120 psi :)

it is more important how a engine is tuned/more then it's cubic centimeter displacement.
example a yz125 would smoke a blaster 200 engine/transmission:eek:
110 or 120 who cares? As long as it runs the way I want it to. If I believe you, I need new upper half so who cares if I burn it up?
 
110 or 120 who cares? As long as it runs the way I want it to. If I believe you, I need new upper half so who cares if I burn it up?

I hope you have unlimited amount of money because with that kind of an attitude towards this machine, your going to be dumping money in it for the rest of your ownership. If you dont believe us and have an who cares attitude, why are you on this forum in the first place? If you already know all, there is nothing we can help you with.
 
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I hope you have unlimited amount of money because with that kind of an attitude towards this machine, your going to be dumping money in it for the rest of your ownership. If you dont believe us and have an who cares attitude, why are you on this forum in the first place? If you already know all, there is nothing we can help you with.
You are all over the map on this one. There are some very knowledgeable blaster owners on this site, I have read some of their posts, that is why I have decided to post here. But by me posting here I get every opinion imaginable and some of those people giving their opinions only think of their own situation/experience which may not be entirely the same as my situation. If I don't agree with everything that ya'll are telling me that doesn't mean I don't respect your opinions. You should expect to have your opinions questioned once in a while. I wouldn't expect anyone to take my advice and never ask me to explain myself. I try to do proper tuning and spend a few bucks on preventive maintenance so that I can ride rather than repair. And I try to buy good engines and keep them good...

With all due respect, that one dude basically said he has seen really screwed up internals that tested better than 110 compression, and said my engine should be 120 and so that difference of 10 is substantial by his standards.

This is the nature of public forums...

There is a MotionPro leak down tester on Amazon for $280 bucks...are you guys renting them from a local shop or making your own?

I appreciate those of you telling me to get a leak test to be safe rather than sorry.
 
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That Motion Pro tester is for use with 4 stroke engines to perform a leak down test. To test the amount of leakage down past the rings into the crankcase.

Unfortunately some people refer to a 2 stroke leak test, as a leak down test, which is very confusing!

A 2.stroke engine is tested by pressurising the crankcase, and the proper term is a " leak test"
 
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i was just pointing out that is a low on compression
run it at 110psi till you cant go anymore:)
most of us on here have 148-155psi
your RUNAWAY IDLE sure is not your compression
but sounds like you solved it with your carb
good job
 
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I have been under the weather for a while now and have not touched the Blaster. I am considering ordering a leak tester, and I may re-do the compression test too because #1) when I did the compression test the pilot air screw was closed but I did not yet know it,(not sure if it will change the result) and #2) my compression tester is old so I may get a new one and re-test it.

Also, when I had my carb apart I noticed there were no O-rings on my float bowl drain screw, can anybody tell me if that is correct? thanks.
 
Finally had a chance to get the Blaster out yesterday. I put the factory airbox lid back on instead of using the ehs racing screen lid. It runs good with the factory lid now that my pilot airscrew is open.

I don't want to put in the time to re-jet it right now, therefore I am not using the aftermarket lid.

There were no O-rings on my float bowl drain screw, is this correct?
 
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