I think I've figured it out! i.e. bogging/loss of power

Discussion in '2-Stroke Engines' started by racereeves, Jun 28, 2008.

  1. racereeves

    racereeves New Member

    I've been so troubled by the fact that as I start to accelerate the engine goes into a very sluggish behavior. It starts to four cycle which makes it perform poorly. My top speed has only been 19 to 20 MPH which takes place at about 3/4 throttle. If I give it WOT it boggs down and I lose speed/power. I've known that It running rich so I moved the needle clip to the very top/end to lean out the mixture only to have it do the same things.
    Tonight I decided to disassemble the carb and really take a good look at things. The first and most important thing I discovered was that as I removed the air filter it was oily. The carb itself was also dotted with drops of oil everywhere. It was obvious that gasoline was being syphoned in to the induct through the bowl vent tube which is located just below and to the left of the choke plate bolt. I havn't run it yet being that it's almost 1am but I believe this to be the root of many of our bogging down issues as the engine's rpm's increase. It makes sense that as the engine pulls in more air the vacume that is created sucks up some gas from the bowl through the vent.
    My solution was to use about three inches of heat shrink tubing and push one end into the vent opening near the choke. I then pushed the tube through the air filter and bend it down so that it was just long enough to stick out the bottom of the air filter cover.
    Again, for those of us (and there are quite a few) who are having this problem, please try this and let me know the results. I look forward to running the bike tomorrow and see for myself. The down side is that the tube doesn't allow the choke plate to cover the air induct but I believe the benefits will outweigh the loss of using the choke.

  2. BSA

    BSA Guest

    Do you live in a hot climate, as if you don't you may have problems starting without a choke in the winter. I'd just clean the air filter and be sure not to flood the Carb next time.

  3. racereeves

    racereeves New Member

    Well...it runs much better. better acceleration and doesn't bog down. I don't use nearly as much fuel either. I think that was the problem. I do understand that living in Ohio necessitates the use of a choke. I'll have to figure something out. Anybody out there trying this? It's been a very satisfying experience to feel the engine cycle properly. I'm not an expert by any stretch of the imagination. In fact, this is my first experience with a two stroke engine. Any other feedback or suggestions would be terrific. Thanks for reading...
  4. Snax

    Snax Member

    I can only say that starting mine in 50F temps with the mixture set at the second notch did not require the choke. In fact, adding the choke just made it bog and not fire at all. With it set at the leanest notch, I need full choke for about 10 seconds and can get it going from there with just the throttle. I think it hurt my top end performance by a hair though and runs it a touch lean at higher rpm.
  5. badmoon

    badmoon Member

    i will try this and tell you if its good cause me too when i was using to much gaz for more speed it was bogging with brrrrr sound i dont like this if you know what i mean .
  6. racereeves

    racereeves New Member

    I took the air filter and cover off just to see what would happen and it took right off. Not getting enough air. It might be that the filter element is pressed up against the induct too. maybe get a different air filter (cone). That would probably do it for you.
  7. fastboy9

    fastboy9 Member

    I have had a breakthrough on my bike, before it was running awfully but I didnt know any different. It use to bog out at full throttle high speed, you know, that same old situation of it hitting about 25 then slowing down to 23 then back up again. Well I took the float bowl off of the carb and found that the jet wasnt screwed in! it was just barely in the threaded hole.

    I took the jet out to make the hole bigger, I think it was this that fixed the problem.

    This is how you do it:
    To make it even easier for you, loosen the clamp on the carb, where it attaches to the intake manifold tube. And see if you can just turn the carb to the side, just more simple that way so you dont have to disconnect the throttle and everything. Next make sure the fuel tap is turned off, and that you have laid some newspaper on the floor under the bike as petrol is likely to spill out. Now unscrew the two screws that hold the bowl on to the bottom of the carb; there will be a lot of petrol in there, so you might as well pour it back into the tank carefully. Do not lose the white float!! From here you will now see a little brass component, this is the jet.

    1. First unscrew the jet from the carb, (the jet is a brass part of the carb with a little hexagonal part on it that allows you to unscrew it)

    2. Now find the end with the tiny little hole in it. This is what sucks the fuel up out of the bowl. At high speed the engine is trying to suck loads of fuel up, but the hole is too small to supply the high demand, so the mixture leans out, potentially damaging your engine.

    3. So get a drill bit or something to widen the hole. It is extremely important to only widen it by the most tiny tiny tiniest litlle bit, too much and you will have negative effects. (It is possible to make the hole smaller again but it takes a long time. Heres a thread that tells you how to do it: http://www.motoredbikes.com/showthread.php?t=5988). The brass is very soft, so take it easy, as more will file away than you think. It is best to widen it by a tiny bit and then test, and keep repeating until the bike is running just how you want it.

    4. Now blow through the jet as hard as you can to get rid of any muck that might have got into it.

    5. Next screw the jet back in to the carb, do not over tighten it as the brass thread will collapse with the most minimal of force.

    6. Now re assemble the carb and take it out for a test ride. If you get the same result as me, then you won't stop riding until you run out of fuel, the difference is amazing!

    I'm going to post this in a few threads because a lot of people having this problem and I'm pretty sure this is the solution.

    Have fun!
  8. acecreeper13

    acecreeper13 Guest


    I tried everything before trying this method. I actually did not drill anything, I just replaced the jet with an old carb i had from an old busted motor. Yea the tiny hole at the end was a hair or two larger! Now it runs smooth. thanks