Rotax 582 front cylinder EGT HIGH

16 posts in this topic

Posted

Can anybody please help me figure out why my completely overhauled rotax 582 blue head is running high EGTs on the front pto side cylinder back cylinder runs around 1000 to 1050 at 4500 rpm and the front wants to climb right up to 1100 and keeps on going if I let it which I have not it's got all rebuilt carbs including all jets needle clip and ECT.. any advice would be greatly appreciated I have already determined it's not gauges it is I tried analog after thinking it could be my EIS please help new motor new prop new glass panel and still on the ground 

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Posted

Carefully inspect the condition of the carb sockets. A crack allowing air in could cause a lean mix. If you're sure that all jets and needles match between the carbs, you could try swapping carbs to see if the problem moves.  

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Posted

Also, could swap EGT probes just to rule them out, unless you did that already.  And also, What do the plugs say.  Can you see that the front plugs are running hotter then the rear ones?  Plugs don't lie.... JImChuk

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Posted

Ya I am going to swap carbs around today and try that and also inspect the carb sockets. I did switch the probes and front still runs hotter hopefully I'll get some answers by switching the carbs thanks 

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Posted

 OK so I swap the carbs and the front cylinder still runs hotter I also swapped the EGT probe's front to rear rear to front  I also tried two analog gauges plus matching it with my EIS and everything seems to match out that the front cylinder still runs hotter all the jetting in the carburetors match and all the needle clips are the same I am at an absolute loss wondering what it could be checked the carbs  Sockets and couldn't find any air leaks. 

Is it possible a base gasket sucking air on the front cylinder thanks 

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Posted

Who did the overhaul, did you run this by them?

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Posted

Well I used rotax Rick and I have asked him a few questions before I ruled out what I know now he was saying it could be the jetting in the carb he said I may need to run a bigger main jet or change the needle but I feel that would do anything but mask a bigger problem I am no two stroke genius that's were I leave it up to all the amazing knowledgeable people on this site 

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Posted

Have you checked for head leaks using soapy spray and turn the engine over or better yet a differential compression checker?

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Posted

I wonder if your front seal is leaking.  There is a way to test that, basically block off intake, and exhaust ports, and pump air into where your pulse line would hook up.  Have a check valve in the line, and see how long the crankcase will hold 3 lbs of air pressure.  Actually the airpump on a blood pressure cuff works real good, cause you can control the amount of air going in.  The seals can't take more than 5 lbs pressure so you have to be careful not to overpressure things.  Here is  a picture of the one I made.  The end of the hose you don't see in the picture goes to the pulse port.  If my memory is correct, there is a pulse port hole near the front of the engine as well as the back one most people use for their fuel pump.  It has a plug in it that you can remove to check the front of the crankcase.  JImChuk

 

IMG_0462 (Large).JPG

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Posted (edited)

 

I might also lean towards a front (PTO) seal. The possibility exists, however, for a seal to leak one way and not the other (i.e. leak in suction and not under pressure - depending on the defect, kinda like a check valve).  Are you running a C box?  If not would he need to remove the gearbox to gain access to a leak area (to verify leakage)?

1Avidflyer -  neat set-up, would your test communicate pressure to the PTO side of the case given the center seal?  Maybe it will work its way through the rotary valve system (intake manifold)?  Guess you could always leave your exhaust manifold on and let it communicate that way.

On the intake side, can the rotary valve cover take 3PSID? 

Other things to look at:  Carb rigging/balance and maybe even prop loading (as an initial mechanical start point, do both throttle slides reach the top of the carb throat at the same time when you go to full throttle?).  Any chance your prop is way under pitched?

Other leak sources: RV gaskets, oil injection lines and fuel primer lines (if you have them), and cylinder base gasket.

Its been a while since I have looked at mine, but any other penetrations on the PTO side case that might be leaking (case drain plugs - not sure of these engines have them) and pulse line, connection tubing, and pump diaphragm (though this I believe is on the mag side).

Isn't 4500 rpm a typical lean spot for these engines (i.e. would it fall back off at a higher RPM)?  Depending on loading, it might not be that far off.

If you havent yet done it, a compression check warm would be a good idea as well.

Edited by LSaupe

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Posted

I dug up the magazine article I had on making the crankcase tester I showed in the earlier post.  Don't think the center seals are the culprit,  they are full of oil from the rotary valve shaft gear area.  If they were leaking however, you would see an increase in pressure on the other half of the crankcase if both sides are sealed off.  The article is kind of hard to read, most info regarding the crankcase testing is in the last colume.  JImChuk

 

pressure test crankcase 1 001.jpg

pressure test crankcase 2 001.jpg

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Posted

Make sure its not something stupid like a dent in the exhaust header too, It would be best to pull the header pipe off and inspect the pistons as well, Make sure they match and are both new, Could just be the way the ports in the engine flow too, Jetting one different than the other is ok, Many many snowmobiles came from the factory that way, PTO side was always hotter because of that hot clutch right next to it, Use to tripple pipe lots of sleds as well,l each pipe would flow different, You adjust it with different size jets,

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Posted

I use the Artic Sparrow mixture control in which I can adjust the mixture manually. One turn of the mixture control is the same as one clip on the needle. I have never had both carbs adjusted the same. One cylinder has always ran hotter than the other. 

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Posted

make sure you sync. the carbs.  Most of the time when I have had one running hotter it was due to the carbs being out of sync.  Amazing how much smoother it is when they are perfectly synced as well.  I got the carb mate sync and love it.

 

:BC:

 

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Posted

Thanks for all the info guys I have lots to try now I determined that the probes are reading acuratly this morning so I know now that's it's a definite carb or engine related problem I will give these things a try and see what I come up with this is some of the temps at 5800 with front carb on factory clip spot and back carb 2nd clip from top 

IMG_0276.PNG

IMG_0277.PNG

IMG_0279.PNG

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Posted

Great thread. Do you have an update on your cylinder issue?

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