|
Post by zbuck on May 24, 2010 10:20:26 GMT -5
Yes a larger carb would work, but with a stock head I would be defeating my purpose. I could pour all the fuel and air to it, but those little stock valves can only handle so much. Also stock cam. I have a buddy that works on vintage motorcycles. He asked me how the scoot was doing. I told him I could only get 6900 rpms. Then he said how many miles since the BBK, I said about five, he said hey dumas do you think that it loosen up after more breakin. then I really felt like a DUMAS. Don B.
|
|
|
Post by Rebel on May 24, 2010 11:07:08 GMT -5
OK, a lot of experts say that if you port and polish the head, you will get as much or more power gain as doing the BBK. You might consider that. then you would need to address the air/fuel issue again.
|
|
jmkjr72
contributing staff
Commander 132nd Northern Cav. Division
Posts: 2,779
|
Post by jmkjr72 on May 24, 2010 21:45:40 GMT -5
no porting and polishing never does any thing except create a lot more power (ok at least on a 2 stroke if you are wise you can double or dan near double your hp with a bit of work)
|
|
|
Post by Rebel on May 25, 2010 0:29:20 GMT -5
an expert has spoken
|
|
jmkjr72
contributing staff
Commander 132nd Northern Cav. Division
Posts: 2,779
|
Post by jmkjr72 on May 25, 2010 19:36:17 GMT -5
polish the crap out of the exhaust side and just clean up the intake you need the turblance on the intake i bet you could get a good gain in air flow just by cleaning up the stock head
|
|
|
Post by zbuck on May 26, 2010 9:05:25 GMT -5
I have all ready ported and polished the head. I even port matched the insulater to the head and the intake manifold to the insulater. Even after doing this with the small valves I am not getting enough fuel and air flow. I have a buddy that builds MC drag engines and he stated to try a cam with more duration and lift? Don B.
|
|
rob
Cadet
Posts: 26
|
Post by rob on May 26, 2010 10:24:55 GMT -5
If you go for a cam be sure to get better valve springs to match it , if you didnt already upgrade when you ported the head . rob
|
|
|
Post by Rebel on May 26, 2010 11:09:31 GMT -5
Sorry, I just went back and saw that you already mentioned porting and polishing the head. At some point you have to ask yourself am I better off just buying a bigger displacement scooter. Seems you have done just about everything to be done to one of these 50's. I know some people want the 50cc for things like not needing a M/C cert and insurance, but really that is not that big of a deal, and you are only going to go so fast on a 4 stroke 50, if you were talking abut a 2 stroke, well that is a different story, those can be made to outrun a 150cc 4 stroke, but it costs bucks to buy and bucks to mod. Here is a link to a cam, runs about $50.00 www.partsforscooters.com/Performance_cam_qmb;jsessionid=0a010c461f4313d569bef882448da253e8bff8e66810.e3eSc3qPbN0Te34Pa38Ta38Rb3n0?sc=11&category=735more thoughts; iridium sparkplug tire pressure 5 - 5.5 gm rollers/sliders
|
|
jmkjr72
contributing staff
Commander 132nd Northern Cav. Division
Posts: 2,779
|
Post by jmkjr72 on May 26, 2010 19:55:40 GMT -5
this is why i love my 2 strokes so much simpler to mod the fudge out of
|
|
|
Post by zbuck on May 27, 2010 9:32:55 GMT -5
When I ported my head, I rebuilt the head with new valves, springs, oil seals and keepers. had the seats redone. Tulip the valves. Rebel, as far as the 150cc, this 50cc is just a toy. My street ride is 08 HD Screamin Eagle. The though of paying 15/16$ for a spark plug is to much, when I can space gap a regular NGK and do the same thing. I am also playing with the tire pressure. I am going to weigh my rollers and go from there. Thank you for the cam link. jmkjr72, I quit working on 2T, 10 yrs, ago. Don B.
|
|
|
Post by Rebel on Jun 1, 2010 12:36:33 GMT -5
|
|
|
Post by 90GTVert on Jun 1, 2010 14:28:18 GMT -5
All of my combos seem to wanna make their peak power in the 7500-8500 RPM range even with an aftermarket cam. I have the NCY cam enviromoto sells. It's got longer durations and steeper ramp angles, but no increase in lift. If you decide on a cam, check piston to valve clearances first. My 80cc kit puts the piston real close to deck at TDC and I've got a couple of bent valves to prove checking clearances is worth your time. Revs go up a little, but I think roller weights are what you need first. I can make mine only wanna rev to 5-6000 RPM with heavier weights. I can put light weights in and get over 9000 revs. Could probably push beyond that with either a lighter rider or a hill.
|
|
|
Post by zbuck on Jun 8, 2010 9:43:00 GMT -5
Rebel and 90GTVert, I apologize for not replying sooner. I have a small engine business and everybody decided that they wanted there lawn tractors and push mowers repaired at once. So I put the scoot on the back burner. Rebel, Thank you for the link. I was playing with the scoot last night, while on the center stand I can get 9800 rpm's. But with my 200 lbs test riding I can only get 6900 r's. I weighed my rollers and they are 7 grams and I marked the variator but have not pulled the cover to check yet. I also set my tire pressure at 30psi. I have decided not to go with the hot cam,but Thank you for the advice. Don B.
|
|
|
Post by Rebel on Jun 8, 2010 11:07:52 GMT -5
pop some 5.5 gm rollers in there and see what happens, I'm pretty sure you'll see a big jump in the rpms.
I'd love to pick your brain about my riding lawn mower that throws belts.
|
|
|
Post by Rocketdog on Jun 8, 2010 19:06:46 GMT -5
I ran 5.5s in my QMB139. It has a larger diameter NCY Variator and the belt will travel all the way to the edge. Even with a yellow 1500 rpm Contra spring.
RD
|
|