OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Full crank stalling when warm, any ideas?

Hi guys, I have a mk4 full crank 160 on a go kart im building. Its currently running a modified g3 carb until I can get a more suitable carb, I swapped the throttle shaft over to one from a briggs and stratton carb to eliminate the gears and their associated issues. The problem I'm having is that the engine stalls after a little bit of running (takes longer if just idling), a minute or so in, it also feels very weak and the acceleration is hopeless, though that may just be the exhaust config.

When the engine stalls it is really hard to get started again and will stall again after a few fires, eventually refusing to start altogether. I replaced the rings in the engine the other day to try and get more power but so far no difference, the crank seals are virtually brand new and the engine is clean internally after a complete strip down and reassembly. The decompressor is being run by a nipple off one crankcase half but doesnt seem to be working aswell as a few days ago, will oil in the decomp screw it up and cause it to stall when running?

I cant think of anything else off the top of my head that would be affecting it, so if you guys can think of a possible solution it would be amazing. If you want photos I have some I can post later.

Thanks

Hi Jordan23,

Go Karts are good fun when they are running Check your points condition and timing; if ok, I'd replace the condenser, if it is a points ignition.

But FIRST.....See if it has spark when it stops, by the sounds of it I don't think it will have. Check with the plug your using, and without it too... it could be just the plug.

I sorry but I dont know what you've done with the carby and exhaust mod, I assume it is ok? How is the float level etc.? Blocked jets? etc.

Photo's are always welcome!

Have fun!

Condenser is Also nearly brand new. I'll try one from a different engine anyway just to rule it out. I'll check the points and timing too, would I be better off switching to electronic ignition? I have everything for it already just havent done it yet. I haven't checked the spark straight after running it, but it does still have spark. Will switch he plug too.

Uploading pics doesn't seem to work from an iPhone. If I remember I'll upload it from my computer later. Basically all ive done is replaced the shaft the throttle plate pivots on with a more standard one so it is actuated like a normal carb not through the 90 degree gears. Exhaust is just a straight pipe to replace a baffled muffler. And the carb seems clean, jet is at least, it runs normal for a little bit so it's likely no that, I'll give it a look over still.

You may have seen the kart, there's photos of it on diygokarts, pretty sure your a member, I'm jman231994. I was reading somewhere that a faulty coil can fail when it warms up? Could that be it?

Thanks for the help

Hi Jordan23,
Yes I've had a look through your photo album on that site but found a VC Mustang which you have done up very nicley .

Seems you have had plenty of advice over the years for your Kart and motor on there! Looks like you have tossed the Tecumseh carby some time ago... probably a good thing....I'm sure we can get your Victa sorted out quickly and going, so you can enjoy your years of saving and hard work from now on!

Try the spark after it stops first! then we can go from there, ONE thing at a time, its easier that way!

Thanks, yep thats the engine, came up nice and shiny haha. The Tecumseh carb was running way too rich so the g3 it was, I'll try to take it for a run tomorrow and get back to you with how it goes

Thanks again for all the help

No worries,

I just had a thought... you have plumbed the decomp into the crank case?..... I think that may give you drama's as well, as they work from carby side vacuum; in the crank case, it pressures up after the inlet port closes....

You might have to "man up" plug the case hose and take the decomp off.. if you can't fit the hose to the carby inlet as per STD G3 arrangement.

I hope it goes well!

G'day jordan23 ..With any mod you do to an engine you only do one at a time then run it if all goes good mod worked if not you know what the problem is,you seemed to have done a few at the same time very hard to work out what the problem is..Me Id take the engine back to stock with stock carb and muffler getrunning good then mod it....Also 2 strokes dont run very good if at all with a straight pipe they would be short circuiting as they call it... Most none race industrial 2 strokes at least have a nice flat front wall made into the muffler for pressure waves to hit and bounce back and push some of the fresh mix back into the exhaust port... A race 2 stroke with a tuned pipe comes on power very hard and fast with a tuned pipe the pressure waves bounce back that fast it is literally supercharging the engine!...good luck you will have it running in no time...Cheers Chris

I can't believe it but when I took the kart out today to check the spark it fired right up and never stopped. I drove it around for half an hour or so, no troubles. It was more powerful too. Chris, I tested the original muffler against the straight pipe and found the straight pipe provided heaps more power, I completely agree with you about tuned pipes however in this case the standard muffler is just too restrictive, open port showed no difference to the pipe. And fastgrass thank you for the help, the crankcase pressure should begin prior to the inlet pressure which when you think about it might make the decompressor preshut which couldn't be a bad thing...either way it works so I'm
Happy

On a side note would anyone have some Specifications for a tuned pipe or megaphone for the victa, I'm still after a bit more performance. Thanks again

Good stuff, it must have been one of those "phantom" type problems ! Ignore the exhaust issue and have some fun with it for a while! Although it might pay to weld on a big Briggs straight through muffler to shut it up, your noise might wear thin with others in ear shot, and they might shut you down (no fun there)

Enjoy the holidays..... sideways

FAST GRASS

I'll help you out with the expansion chamber design... much later... but first a video of your engine/kart would be good, feel free to PM me...

Nah, theres a big open area where my local council keeps their soil and stuff at the top of my street, theyre rarely there and its far enough away from all the houses to not be an issue.

I will enjoy the holidays sideways, it drifts nicely haha

Ill post some videos in the coming week or two, I figure brakes would be a good addition before I film myself hitting a tree or something haha And yea, I may never bother to make a proper exhaust for it, just tweak the straight pipe to make it run better, but if I do I'll be straight in search of you haha

Thanks again for all the help, video will be up soonish, and enjoy the holidays too