Need help tuning/troubleshooting bike

EvanT

New Member
Sep 11, 2020
1
0
1
20
TL;DR: Bike seems to work fine with the clutch disengaged but won't give any power under load (while riding).

To start off, I'm relatively inexperienced in working with gas engines, so I need some help diagnosing some problems I'm having with my bike. I've read countless forum posts trying to figure it out myself, but I think I just need a little more experience before I can be sure I know whats going on. (^)

I built my bike about a year ago with one of the standard 2-stroke kits off of Amazon and it ran perfectly. Once warmed up I could quickly hit speeds in the upper 20s. Not satisfied, I recently bought a Dio Reed valve, a windowed piston, and an OKO carburetor (which I assume is a clone because it was extremely cheap) and installed them on the bike. Now, with some playing around, the bike will idle fine (although sometimes the idle will take off out of nowhere and I'll have to cut the engine), and will even rev to high rpms with the clutch disengaged but will not rev at all under a load. When riding and giving it a little throttle, the rpms immediately drop and it sounds almost guttural before dying out completely. If I play with the choke a little while riding I have slightly more success, but it still sounds the same and I can get it to maybe 1/3 throttle before the problem resurfaces. I'm using around a 20:1 gas/oil ratio since I replaced the cylinder and need to break it in again.

I thought maybe it was starved of fuel, so I'm using the largest main and pilot jets I have (125 and 41 respectively) with the clip on the middle notch on the needle, though I've tried many different combinations of jets/clip positions to no avail. I'm sure there is no problem with fuel flow through the filter, so I'm thinking my issues are due to the bad carburetor? Also, I've given thought to a possible air leak somewhere, but I don't know where it could be and don't know exactly how to check for one. My spark plug is completely black but it is a year old, so I don't know how much reliable information I can get from it. For all I know, it could instead be too lean, but regardless, I'm out of ideas and really don't want to give up. I'd really appreciate any feedback or ideas to try next!

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carburetor al

New Member
Jun 14, 2020
9
1
3
72
TL;DR: Bike seems to work fine with the clutch disengaged but won't give any power under load (while riding).

To start off, I'm relatively inexperienced in working with gas engines, so I need some help diagnosing some problems I'm having with my bike. I've read countless forum posts trying to figure it out myself, but I think I just need a little more experience before I can be sure I know whats going on. (^)

I built my bike about a year ago with one of the standard 2-stroke kits off of Amazon and it ran perfectly. Once warmed up I could quickly hit speeds in the upper 20s. Not satisfied, I recently bought a Dio Reed valve, a windowed piston, and an OKO carburetor (which I assume is a clone because it was extremely cheap) and installed them on the bike. Now, with some playing around, the bike will idle fine (although sometimes the idle will take off out of nowhere and I'll have to cut the engine), and will even rev to high rpms with the clutch disengaged but will not rev at all under a load. When riding and giving it a little throttle, the rpms immediately drop and it sounds almost guttural before dying out completely. If I play with the choke a little while riding I have slightly more success, but it still sounds the same and I can get it to maybe 1/3 throttle before the problem resurfaces. I'm using around a 20:1 gas/oil ratio since I replaced the cylinder and need to break it in again.

I thought maybe it was starved of fuel, so I'm using the largest main and pilot jets I have (125 and 41 respectively) with the clip on the middle notch on the needle, though I've tried many different combinations of jets/clip positions to no avail. I'm sure there is no problem with fuel flow through the filter, so I'm thinking my issues are due to the bad carburetor? Also, I've given thought to a possible air leak somewhere, but I don't know where it could be and don't know exactly how to check for one. My spark plug is completely black but it is a year old, so I don't know how much reliable information I can get from it. For all I know, it could instead be too lean, but regardless, I'm out of ideas and really don't want to give up. I'd really appreciate any feedback or ideas to try next!

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Try a smaller main jet.Clean the spark plug. See if your exhaust is all gummed up from running rich.