chrisnbush
Member
I posted some of this on a related thread (search dellorto) but as it was getting long and a little off topic, thought I would put a summary here. I have seen a lot of posts about weak 80 cc engines. I have (had) one, that I got from DAX, the largest of the 3 sizes he sells. I won't get into the argument about what the displacement actually is, I believe it to be the largest available as DAX sells three sizes (starting with 49) and I don't think Duane would sell them as 3 different ones if they weren't.
To recap: I have improved this "80" cc motor which was weak from Dax, by first grinding open the exhaust pipe entrance (on the pipe) to more closely match the engine port, and also the input side (which didn't make much of a difference).
I improved it further by also drilling a couple of holes in the baffle, and bendingthe internal routing plate in the exhaust to make more of a straight shot for the exhaust. Louder, but improved power. Low end torque now takes me up any hills. BUT still not running as high as an RPM as other engines have for me.
SO, as my plug is usually wet, even with the carb needle now as low as it can go (this is the "standard" NT carburetor I guess built for the 49cc engine if this is to be believed), I ordered a set of carb jet drills off of ebay, soldered my main jet, and attempted to drill it out to like 55 or something. Failure, as the drill chuck in this cheap set was ****, and I am not very patient and broke some drills.
I purchased the 5mm Dellorto jets, got a 55, 60, and 65 - understanding that the stock jet is somewhere around 70 - 79. They came last night ! I am telling you the stock jet looks real close to 65 so now I am thinking that it might be 70 instead of 79 as I have heard through others.
In ANY event, I put the 60 jet in, and there is quite a bit of difference. Still 2 strokes at higher RPM, but at least it goes to higher RPM - I can tell I will get a lot more speed out of it. And low end is even better than before, I declare this bike a winner now.
So, I would recommend "matching" the exhaust pipe to the engine port, drilling some holes in the muffler baffle / or purchasing an expansion pipe, and REDUCING the main jet size for weak 80 cc engines (if the PLUG is wet after running at higher RPM for a couple of minutes). My somewhat lower cost approach.
Just in case this helps
BigKid
To recap: I have improved this "80" cc motor which was weak from Dax, by first grinding open the exhaust pipe entrance (on the pipe) to more closely match the engine port, and also the input side (which didn't make much of a difference).
I improved it further by also drilling a couple of holes in the baffle, and bendingthe internal routing plate in the exhaust to make more of a straight shot for the exhaust. Louder, but improved power. Low end torque now takes me up any hills. BUT still not running as high as an RPM as other engines have for me.
SO, as my plug is usually wet, even with the carb needle now as low as it can go (this is the "standard" NT carburetor I guess built for the 49cc engine if this is to be believed), I ordered a set of carb jet drills off of ebay, soldered my main jet, and attempted to drill it out to like 55 or something. Failure, as the drill chuck in this cheap set was ****, and I am not very patient and broke some drills.
I purchased the 5mm Dellorto jets, got a 55, 60, and 65 - understanding that the stock jet is somewhere around 70 - 79. They came last night ! I am telling you the stock jet looks real close to 65 so now I am thinking that it might be 70 instead of 79 as I have heard through others.
In ANY event, I put the 60 jet in, and there is quite a bit of difference. Still 2 strokes at higher RPM, but at least it goes to higher RPM - I can tell I will get a lot more speed out of it. And low end is even better than before, I declare this bike a winner now.
So, I would recommend "matching" the exhaust pipe to the engine port, drilling some holes in the muffler baffle / or purchasing an expansion pipe, and REDUCING the main jet size for weak 80 cc engines (if the PLUG is wet after running at higher RPM for a couple of minutes). My somewhat lower cost approach.
Just in case this helps
BigKid