Still too rich.

Discussion in '2-Stroke Engines' started by OTP, Jul 5, 2016.

  1. OTP

    OTP New Member

    Ive got a new Grubee Skyhawk GT5A that runs too rich. Since I live on the side of a mountain and weigh 250 pounds, I bought a hub adapter and 50 tooth sprocket from MZMIAMI parts to go on my 700c wheel. I broke the engine in on the 1/4 mile of reasonably flat dirt road by house with the recommended 16:1 mix. What a dripping mess. It was 4 stroking terribly with the stock 70 jet so I ordered a 68 and a 66 from SBP.

    I put the 68 jet in my NT carb and took off on a 60 mile ride still with the 16:1 gas. I was able to climb pretty big hills that I never would have been able to without the engine's help but it was still 4 stroking on anything but an uphill grade.

    Now I've got the 66 jet installed and I'm running 32:1 mix but it's still not running right until I have a pretty good load on it going up hill. By the time it starts running right, I've lost most of my momentum.

    I've read the hell out of these forums and have gone over everything I could think of. Float is correct, there are no settings on the needle, everything is tight, running NGK B7HS plug, I even poked a long screw driver through the mesh screen inside the muffler in an attempt to increase the airflow. That seemed to help a little but the thing is still getting too much fuel.

    I don't want to go fast, I just want the engine to run as it should. Is it safe to go smaller than a 66 jet? Is it possible the thing is geared too low and doesn't have enough load on it with the 50 tooth sprocket? I'm considering trying the stock sprocket just to see what happens.
    Last edited: Jul 5, 2016

  2. Frankfort MB's

    Frankfort MB's Well-Known Member

    If your running rich then there's no way to get around it unless you put a smaller jet in the carb. Try taking air filter off too know for certain if your running rich, that would lean it out and should have the right mixture then
  3. crassius

    crassius Well-Known Member

    2-strokes are peaky, such that one needs to feel for a throttle point that will give good 2-stroking uphill, then open throttle slowly as motor picks up speed

    that said, if the bike is very peaky (2-stroking point very low on throttle), it may be too rich in the 1/4 to 3/4 throttle positions where dropping the needle will do more good than changing the main jet - one may also drop the float level just a bit to help
  4. jaguar

    jaguar Well-Known Member

  5. OTP

    OTP New Member

    Thank you all for your replies.
    I had the opportunity to go for a test ride beyond my little quarter mile of dirt road today and I guess I'll have to accept my engine the way it is.
    Most of my ride was on single lane rolling back roads but I was able to wind the engine out and get some decent speed. I could probably use a carb needle with some adjustment since mine has none but I think I am happy enough with the 66 jet. I saw a needle for sale on thatsdax website (he needs to kick his webmaster's ass, lol) but I can't tell from the picture if it has the adjustment rings or not. I'll look around.

    I think the engine is finally getting broken in because the last leg of my journey was on a flat two-lane road and I was holding the throttle wide open just letting it eat while trying to get home before dark. I was able to hit ludicrous speed that scared me enough to back off before it blew up and I turned on a GPS app to measure the speed. Six of the ten miles showing were from earlier.
    30 MPH with 50 tooth rear sprocket??
    I'm not sure how accurate this is since with Jim Sitton's ratio calculator, I figured my top speed to be 23MPH at 6000 RPM but my engine was absolutely screaming and sounded like a beast. That reminds me, I need to start cutting firewood.

    Jaguar, I have read a lot of your posts here and on your dragonfly page and I've learned quite a bit, thank you for that. Two things stood out in my memory before I even started this thread.

    "Four stroking will also occur in a correctly adjusted two stroke engine at wide-open throttle without load [ie: going downhill or reaching top RPM without upshifting]."

    "This quote is from a chainsaw forum: "The proper tune for a chainsaw is to run it rich enough to four-stroke at wide open throttle with NO LOAD, but to smooth out the instant load is applied.""

    I read what you had to say about your CDI and was ready to buy one until I saw the price. I really am impressed that there are people like you out there who are enthusiastic enough about these engines to use your talents to create such upgrades. My bike has nickel and dimed me enough already just to get it to stay fastened to the the damn frame and not drop parts on the road (AS IT SHOULD HAVE BEEN OUT OF THE FUGGIN BOX!) Regardless of how your CDI may help and as much as I like to get retarded myself on occasion :confused:, there is just no way I am willing to put so much more money into such a POS engine. Sorry.
    Last edited: Jul 6, 2016
  6. jaguar

    jaguar Well-Known Member

    yeah but it will be less POS with a good ignition system.
    Then just balance the crank and you will have little to complain about.
  7. crassius

    crassius Well-Known Member

    if for some reason your carb needle has no adjustment, it will be hard to find a needle of correct length & taper to work - there are MANY needles out there that all fit, but run much differently - few people have ever had much luck with running the wrong needle for their carb (cheaper & easier to buy a diff NT carb that has adjustable needle instead of that NTSPEED carb you seem to have in the pic
  8. OTP

    OTP New Member

    Interesting that the needles are different. My carb is a regular NT, not speed. I do wonder why the air cleaner is different than most and the needle has no adjustment but I think I'll just let it be and ride the thing. The four stroking is mostly at or below half throttle or under light load with full throttle so I suppose that's OK. I had a blast yesterday and was able to pedal up almost every hill I encountered in second gear. I have a granny gear on my rear freewheel but it's too slow to keep the engine RPMs up.
    mftz31.jpeg Is there smaller front sprocket available for the 66cc?
    I really like the idea of a shift kit but I think I'd rather do that with a 4 stroke.
    I'm going to need a bigger garage.