Hey everyone,
This is a repost from my build thread, I thought it might be more appropriate for this section. My build thread:
http://www.dotheton.com/forum/index.php?topic=59122.0
I'm trying to figure out some tuning issues. I've got a feeling that the bike is not running at its best. I got the carbs dialed down as best I can, it purrs like a kitten at idle, revs up pretty good under load, but as for top speed and power its lagging, feels gutless and weak going up hills.
I mean I know its only a 175cc, but I hit 55mph in 5th gear and its damn near close to revving its head off. I get up to 60mph eventually, but the rpms are so high after riding about 20min, the engine gets really hot (pulled up to a light and the motor was steaming).
Also going up moderate hills I get about 25-30mph in 3rd with pretty high rpms. In general, just feels very underpowered and sluggish. Also, I bet the fat tires, 4.00 rear and 3.25 front, are not helping me go faster. (oh and I am 170lb).
I'm guessing the home made baffles (see my build thread) might be restricting the exhaust.
Here is what I have done so far to the engine to make it perform better:
- adjusted the cam chain
- adjusted the valves to spec
- adjusted timing
- cleaned the carbs
- adjusted the float bowl to spec
- synched the carbs to a point where the throttle response is nice, sharp, and even
- dialed the air and idle screws to where it purrs nicely at idle
- installed stock air box filters, nice and tight clamps so no air leak there
- new exhaust crush gasket installed
- Main Jet is at 90
- Slow Jet is at 38
- Jet needle is set to the middle setting
- starts without a choke, rarely needs it
- compression was measured around 135psi both cylinders.
I tried to play around with the float bowl and jet needle setting but all it did was foul the plugs or too lean, no improvement in power.
I tried running without the baffles, just straight pipe, and it ran way worse, absolutely no power and loud as hell, extremely annoying.
So, my plan is to fit the 12" shorty mufflers from dcc with a reducer kit to fit the 35mm(1-3/8") OD pipes.
http://www.dimecitycycles.com/chrome-12-inch-shorty-muffler.html
Hopefully it will reduce the annoying loudness open up the pipes. I would also have to go up on the jets. But at this point will the stock air filter become a restriction? Will pod filters be better with open pipes and jetting up?
Here is the pic of the plugs after running for a few weeks:
I also thought about changing the sprocket tooth ratio to get more top speed, but then the bike feels so underpowered, not sure if that will do any good.
Please chime in with your recommendations and suggestions. I really am clueless when it comes to tuning. Learning as I go here.
Thanks guys!
This is a repost from my build thread, I thought it might be more appropriate for this section. My build thread:
http://www.dotheton.com/forum/index.php?topic=59122.0
I'm trying to figure out some tuning issues. I've got a feeling that the bike is not running at its best. I got the carbs dialed down as best I can, it purrs like a kitten at idle, revs up pretty good under load, but as for top speed and power its lagging, feels gutless and weak going up hills.
I mean I know its only a 175cc, but I hit 55mph in 5th gear and its damn near close to revving its head off. I get up to 60mph eventually, but the rpms are so high after riding about 20min, the engine gets really hot (pulled up to a light and the motor was steaming).
Also going up moderate hills I get about 25-30mph in 3rd with pretty high rpms. In general, just feels very underpowered and sluggish. Also, I bet the fat tires, 4.00 rear and 3.25 front, are not helping me go faster. (oh and I am 170lb).
I'm guessing the home made baffles (see my build thread) might be restricting the exhaust.
Here is what I have done so far to the engine to make it perform better:
- adjusted the cam chain
- adjusted the valves to spec
- adjusted timing
- cleaned the carbs
- adjusted the float bowl to spec
- synched the carbs to a point where the throttle response is nice, sharp, and even
- dialed the air and idle screws to where it purrs nicely at idle
- installed stock air box filters, nice and tight clamps so no air leak there
- new exhaust crush gasket installed
- Main Jet is at 90
- Slow Jet is at 38
- Jet needle is set to the middle setting
- starts without a choke, rarely needs it
- compression was measured around 135psi both cylinders.
I tried to play around with the float bowl and jet needle setting but all it did was foul the plugs or too lean, no improvement in power.
I tried running without the baffles, just straight pipe, and it ran way worse, absolutely no power and loud as hell, extremely annoying.
So, my plan is to fit the 12" shorty mufflers from dcc with a reducer kit to fit the 35mm(1-3/8") OD pipes.
http://www.dimecitycycles.com/chrome-12-inch-shorty-muffler.html
Hopefully it will reduce the annoying loudness open up the pipes. I would also have to go up on the jets. But at this point will the stock air filter become a restriction? Will pod filters be better with open pipes and jetting up?
Here is the pic of the plugs after running for a few weeks:
I also thought about changing the sprocket tooth ratio to get more top speed, but then the bike feels so underpowered, not sure if that will do any good.
Please chime in with your recommendations and suggestions. I really am clueless when it comes to tuning. Learning as I go here.
Thanks guys!