Hey guys, need some help dialing in the tune on my HS. I'm running a Dellorto SHA clone with a #80 jet. It rips on the straights, but I soon as I come to a hill it loses all power and throttle response. I have to keep the throttle pegged open to even get up the hill, usually with a bit of pedal assistance. I can't figure it out, I feel like I may to need to drop down one more jet size, but I also have a feeling the carb isn't getting enough gas to the bowl fast enough. The one downside to these SHA clones is you can't adjust float height. Anyone have a hunch or some info? It's so close.
Need tuning help! HS49
- Thread starter JCraven94
- Start date
Usually when you install a 2-stroke carb on these 49cc 4-stroke engines, you have to install a BIGGER jet to make the engine run properly.
Also... when you say "I also have a feeling the carb isn't getting enough gas to the bowl fast enough"; what that actually is is not enough gas moving past the too small jet. 
Well, I sized up my jets from a 65 when it was on my 2 stroke all the way to an 80. I was at 85, but that was too rich, started bogging out, wouldn't even run with the choke on cold, plug chop confirmed it with a very dark plug. So I backed it down to an 80 and on level surface it cruises, snappy throttle, good power. I was theorizing that either, A) The bike is still running a tad rich and may be flooding with fuel when under load with the throttle wide open (but I feel this isn't the culprit since I've leaned it out, and it runs fine on level surface) or B) When the motor comes under high load, the carb can't supply enough fuel to the larger jetting. It's kind of contradictory I know, but I'm still gathering my database on carburetor tuning and how the engine will tell you what it needs. I have a pretty good understanding of the core concepts, but I'm by far no expert. Just trying to feel it out through the seat of my pants and gut feeling really haha.
