put put burp backfire! help!

walander

walander

New Member
Ok, so I just built two more bikes, both grubee 49cc, this is my 4th and 5th build, but im having an issue with both of them, they both start and run ( sort of) but they both sputter and burp, sounds like backfiring, it will run ok for a few seconds, then a spurt of burps and backfires, I noticed that they seem to do better going uphill, first time I have had this happen and its on both bikes, so im wondering if it has something to do with the weather? I know they run poorly in the cold, they are stored outside but in a barn ( I know they should be inside, but I dont have room ) I was wondering if its water in the gas, the gas I put in both of them has been sitting in my can ( premixed) for a month, The temps outside have gone from the 40's to -20 and now back to heavy snow and in the 30's, could all that change in weather have added moisture to my gas? any advice helps. thanks
 
Mine is doing the same thing and I'm in sunny Florida. It's runs great at half throttle but then it bogs down at WFO. Done all of the tricks except braking into the carb. Still doing research. Don't think i have an air leak because the spark plug looks good. According to what I've read of how it should look. Will play and tinker tomorrow.
 
I would think you guess about water in the gas is a logical conclusion given that both bikes have the same gas and are doing the same thing. It's a hassle, but drain them and try some fresh gas. Let us know what you find out. Good luck, Dan
 
I,m having the same exact problems backefire and a good run at half speed then when i try to get a full throtle run it starts to bog down and or backfire.
 
Ok, so I solved this problem along time ago,but I can tell you now, its 99% likely that its your carb, CNS that comes with the grubee kit right? swap it for an NT or buy manics billet intake. problem solved
 
yes it was the 2stroke grubee skywawk engine ive been looking on line at spooky tooth and they have an NT for 25$ and from what i was seeing this one looks too be a better carb so I'm gonna splurge and do sum shoppin we dont have any shops around where I am from these bikes are jus coming around the scene and getting popular or should i say alot of raised eye brows. so thanx for your emput im sure i got many more questions to post in the future
 
while the carbs are crap in my opinion the real culprit is water in the gas in my opinion also switch it out with fresh im guessing you'll
run great been there got bad advice done that lol
 
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