Purple Haze
Active Member
Play around with the needle height, that really affects part throttle. Mine runs best with the lowest setting (clip in top groove)
Cold weather screws up engine - carburetor air/fuel or jetting?
- Thread starter RB55
- Start date
LewieBike
Well-Known Member
Two strokes, especially piston ported ones, have issues when the temperature drops below 30 degrees. SAAB 2 cycle cars come with an exhaust collector with an air heating attachment that is a tube running to the aircleaner's snorkel, feeding it warm air from the exhaust casting.
I've owned two SAAB strokers, both needed this attachment fitted to run right in cold weather. It may be carb icing and it also might just be denser air leaning the mixture. But it's a proven fact that changes in temperature effect 2 stroke tuning.
You might see if you can make some sort of sheet aluminum duct to channel warm air from the head casting to the intake tubes on the aircleaner
I've owned two SAAB strokers, both needed this attachment fitted to run right in cold weather. It may be carb icing and it also might just be denser air leaning the mixture. But it's a proven fact that changes in temperature effect 2 stroke tuning.
You might see if you can make some sort of sheet aluminum duct to channel warm air from the head casting to the intake tubes on the aircleaner
Frogslayer
Well-Known Member
It won't affect your bike that much. You must be right on the lean edge. Maybe drill out to .62 or. 63 mm bit . Dude it's been around -10 here the last few days and I've been snowmobiling, mopedding, and chainsawing. All piston ported 2 strokes.
LewieBike
Well-Known Member
As long as it's relative humidity dry yeah they run, maybe OK . When the weather turns to snow in the PacNorWet, engine carbs ice up and piston ported two stokes especially. SAAB wouldn't have made that special snorkel device if it wasn't an issue. Been there got the experience in years..
P.S. Snowmobiles and chainsaws are forced air cooled and have their engines cowled inside a compartment and are kept warmer by the engine's heat.
RB55
Active Member
Checked it carefully and everything seems fine, fuel flows when the float is down and flows stops when the float is up. No leaks.
RB55
Active Member
The engine runs great at WOT now but kind of 4 strokes a bit too much at lower throttle settings. That's the most important issue resolved for me since I'm practically always running full throttle 
. I'm going to raise the needle clip to the highest setting, that should help with the lower throttle ranges. It's really more of a noise and vibration issue anyway since it makes that really annoying BRAPPPPPPP-PAAP-PAAP when it 4 strokes. My custom exhaust is already too loud so I don't want the occasional 4-stroke to make that worse...going to repack muffler over the weekend!
. I'm going to raise the needle clip to the highest setting, that should help with the lower throttle ranges. It's really more of a noise and vibration issue anyway since it makes that really annoying BRAPPPPPPP-PAAP-PAAP when it 4 strokes. My custom exhaust is already too loud so I don't want the occasional 4-stroke to make that worse...going to repack muffler over the weekend!
RB55
Active Member
Clip at highest setting now, it runs slightly better at mid to low throttle ranges now. 4-strokes a bit but for these 70$ Chinese engines I'm grateful it even works. Onto more mods! It is a shame though that these carburetors all come rich from the factory. I live at sea level and decreasing the jet size from the factory 0.70mm to 0.61mm is a pretty large drop...honestly stupid on the manufacturer's part. I guess since they just dump 10W-30 or 10W-40 engine oil from decommissioned cars at the junkyard into the gas tank as a "gas/oil mix" they probably need to re-jet their carburetors to run very rich. 
It would be nice if the carbs came with a 0.65 mm or 0.66mm jet instead of the stock 0.70mm....
It would be nice if the carbs came with a 0.65 mm or 0.66mm jet instead of the stock 0.70mm....
You mentioned the price of engines, they have come down a lot since I bought my first. My first kit was a 48cc grubee kit that cost $171 in December 2010, I had to buy 5 to get that price. Some people don’t like grubee engines but the ones I got have been great, I’m still running that original engine with one rebuild.
RB55
Active Member
Good point, even 4 stroke engine kits go for $160 now on eBay, heard they used to be $300+. Maybe I’ll build a 4-stroke next...2-strokes are awesome for power and speed but 4-strokes are much quieter and smoother with a centrifugal clutch as well...with a good bike and mounting along with packing the stock exhaust, it will be super quiet and smooth, great for just cruising around on a nice day without wanting to go fast. 2 stroke when you have that itch for speed and wanna rip!
