New carb and engine, still no power

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yzinger02

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So I bought an MT non running as a project and then put it all together. Got it running but it ran like crap (hard to start, no power, won't increase in revs). So I put my finger over the spark plug hole and pulled and saw it had low compression. So I put a new piston and cylinder on it and then had the same issues, although it was easier to start. Then I put a new carb on I since it had been sitting a while and still same issues, even though it starts and runs a little better. But it still has no power and won't get over about 10 mph unless going down a hill. If I hold it off the ground it'll rev all the way through the range. I'm using 91 pump gas with royal purple synthetic 2t oil (same that I run in my dirtbike, good stuff) and have tried fresh fuel. I don't have the fuel lines reversed, I can tune the carb all I want and it still has no power. Starts right up and then it's a snail. What else can I try? Plug has good spark as well and everything is sealed nice and tight.
 
Oh and it also has an aftermarket pipr, unsure of what brand since I bought it like that.
 
I've reset it probably 100 times. Both screws 1 1/8 turns out but it doesn't matter where the needed are. Still runs like crap. It doesn't stutter and die it just has no power.
 
What carb are you running on it? I have a old stocker that I would have to lein the HSN out big time to get it to tune... It may be your issue also.
 
I've tried nearly every possible needle position. It only gets worse, I've found where it has the most power and any adjustment after that made it worse. But that point still sucks. And I'm running a walbro 40 something if I remember right. Nothing crazy over stock
 
If it will rev off the ground threw the complete power band but when you set it on the ground it goes slow have you check the grub screws behind your gears? To make sure they are not slipping?
 
The clutch shoes might be glazed, but it runs fine if it's going down hill. If it has a little help it'll get up to speed. And which grub screws are you referring to? Because I have it apart right now to replace the clutch bell since the shaft broke when I took it apart to see if anything was binding. I'm pretty sure my tank is vented, when I open the cap I don't hear any hissing and it doesn't make a difference in power.
 
The grub screws that are on the square the holds the square hub on the shaft that the gears fit on top of. If the grub screw is not tight down on the flat part of the shaft they will not spin the gears when under load when on the ground.
 
yzinger02 said:
I've tried nearly every possible needle position. It only gets worse, I've found where it has the most power and any adjustment after that made it worse. But that point still sucks. And I'm running a walbro 40 something if I remember right. Nothing crazy over stock
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Definitely don't want to rule out the set screws....it bit me in the beginning lol. What are the factory base needle settings on the carb you put on ? You say the carb is a walbro 40 something.... We need to know the series # to get that at the right place as a base to eliminate that factor..... Where did you get the carb from?
 
I got it from large scale rc and it's a walbro wt668. Sorry guys. And it has good response of the bottom and then starts stuttering and 4 stroking once I get into the gas no matter where I have the high speed needle set. I'll check tose grub screws though!
 
I replaced the intake gaskets when I put the new piston and cylinder on it. If i lightly sand the clutch shoes would that be a good way to unglaze them without having to replace them?
 
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