I'm working on a Toro single stage snowblower with a Techuseh 5.5hp engine. (LH195SP). Its low hours but sat for awhile. The orginal carburetor was destroyed from sitting with bad fuel so I ordered a new one. It starts up fine but without a load on the engine it surges and pops a bit. If I engage the augar and tio it a bit so the paddles hit the ground to load it up it runs great. As soon as there isnt a load it surges and pops again. I replaced all the intake gaskets as well. Next I decided to try an adjustable carburetor that was offered for it. Same problem but I'm able to get it a little better. Adjusting the high speed screw seems like it puts it either way too rich or way too lean. I can get it close but not great. Adjusting the low speed screw does very little with the problem. From what i can see, all the governor springs are good and set where they should be. New spark plug and fresh fuel as well.
This is a 4 cycle engine.
Any ideas?
#2
Scrubcadet10
Surging usually a lean running condition, too much air or not enough fuel,
I use WD40 in a trigger sprayer and saturate the intake area with it, if it blows white smoke or changes engine speed, air leak.
Also, does it smooth out when you apply choke?
If it still surges with a new carb and you can find no air leaks, I’ll be looking at one of two things. First would be a bad carb or not the carb for your engine. This would be especially true if you purchased on of the Chinese clones out there, as they are built for multiple engines and not engine specific. I have also found that many of today’s Tecumseh carbs come from the factory with the float level set too lean. Might have to adjust the float level slightly richer. If you purchased an OEM carb and you checked the float level, I would then check to see if the governed top speed is set correctly. Most people don’t realize that an improperly set governor can lead to surging.
So the first carburetor was an OEM one from Tecumseh. The second one that's adjustable is an aftermarket one, which could be why it still isn't right. But it does run fairly better with the adjustable one. So I did check for air leaks using some brake cleaner and an unlit propane mini torch but I couldn't find any. Both intake gaskets are new as well. It kind of smooths out a very little bit with the choke in various positions, but it ends up running rich after a few seconds and wants to bog down, even on less than half choke with either carburetor. I did try to adjust the float level a bit both ways but it didn't seem to make any difference.
I did try to adjust the governor screw a little bit both ways as well and it runs better when it's at a lower RPM but it would be too low of an engine speed to make the blower usable.
