Some generic 66cc eBay kit, B6HS plug, stock carb, slide one notch down from top, 16:1 oil ratio for break-in. I'm thinking it's way too much oil, but even then I'd never expect one of these to be this lean. Plug chop attached for the perusal of those more knowledgeable than I; to me, it looks like I need to double-check the float height, then lower the clip a couple notches, then dilute the fuel a little more (is 32:1 okay for break in?), then order some main jets. Also, the heat mark on the ground strap looks like it's way too far over; is 6 really the recommended heat range for these, or is it just getting that hot?
Ever seen one of these things run lean?
- Thread starter thebook92
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FNTPuck
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These motors are usually rich out of the box unless there is a leak somewhere.
Try 32:1 and go over the common vacuum leak spots to be sure there isn't any extra air coming in (carb to intake seal, head gasket, case seal behind magneto, etc).
Try 32:1 and go over the common vacuum leak spots to be sure there isn't any extra air coming in (carb to intake seal, head gasket, case seal behind magneto, etc).
gary55
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Some say 32:1 is OK. I go 6 ozs. Per gallon on break in. B6 is OK. I use B7. How is it running? Does it balk when you snap the throttle wide open then rev real fast and take a long time to return to idle? Does it have a high idle that cannot be adjusted down with the idle screw? Is it hot.
Super lean conditions are not that common unless things like a carb not being all the way onto the intake, Loose intake, loose head, loose exhaust, blown crank seal, bad float adjustment. 21mm.
View media item 61838
Super lean conditions are not that common unless things like a carb not being all the way onto the intake, Loose intake, loose head, loose exhaust, blown crank seal, bad float adjustment. 21mm.
View media item 61838
I did double-check the intake and exhaust bolts before posting, all were tight. Carb-to-manifold I didn't, I'll look again in a bit. This engine has the cylinder and head all cast as one piece, oddly enough. Not something I've encountered before, but at least it's one less place to leak. If I don't find any leaks, I'll look at the float height, then dilute the fuel to 32:1.
@gary55: it idles okay off choke (though it's a b**ch to start cold), idles down to the point of dying completely on choke, lean bogs a bit on the needle, stumbles a little on transition from 3/4 to WOT, then seems to get even worse WOT.
@gary55: it idles okay off choke (though it's a b**ch to start cold), idles down to the point of dying completely on choke, lean bogs a bit on the needle, stumbles a little on transition from 3/4 to WOT, then seems to get even worse WOT.
extremeodd
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My first engine was one of those single piece cylinder/head units, it was a complete turd compared to something like a zeda 80. It had all of the issues your mentioning. The best you can do is make sure the carb is sealing well and try your best to get it tuned in. Worst case, throw a better carb that has better adjustability on to make life a touch easier (or harder if your not good at tuning a carb).
gary55
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Sometimes it's more than 1 thing. Just finished a complete parts swap for a customer with a broken frame to a donated bike.After ironing out all the problems on the fit to new frame the engine ran like crap. Acted lean with no load, and acted rich while riding. Found the leg of the intake where the carb fits to be 13mm long and the carb needing 15.4mms to seat all the way on. Replaced the intake and then it acted rich everywhere. Dropped jet 2 sizes and bingo it's good everywhere. So the slight intake leak along with the oversized jet gives conflicting symptoms.
Everyone has their own way of torubleshooting air leaks. I prefer the unlit torch as it is usable for the seal behind the rotor magnet without worry of shorting out the mag with water.
Everyone has their own way of torubleshooting air leaks. I prefer the unlit torch as it is usable for the seal behind the rotor magnet without worry of shorting out the mag with water.
Ya they seem to be overly sensitive compared to 2 stroke dirt bikes. I had a 70 bultaco 125 Sherpa S with the Amal carb that would load up. You'd have to shut the petcock off til it screamed then turn the gas back on before it died
Found an intake leak between the manifold and jug. Hit it with some RTV, and it seems to be okay. Big one, however, is where the carb clamps onto the intake. The carb seems to seat okay, and the clamp does get tight (to the detriment of the OEM clamp screw, but a drill and 1/4-20 bolt I had laying around fixed that), but if I spray some brake cleaner around the clamp it immediately dies. What's the least bad way to go about sealing that?
Also, my spark plug gap keeps closing up between plug chops. Any ideas as to why that's happening?
Also, my spark plug gap keeps closing up between plug chops. Any ideas as to why that's happening?
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gary55
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I don't have problems with leaks on the NT carbs once they are firmly seated on the intake, but some say they do.You can see some small cuts in the carb inlet beneath the clamp. You should be able to see the intake slide past the end of those cuts to make sure it is seating all the way on. Some get a small Oring and put it in the inlet of the carb for a better seal. I believe it would be a 19mm OD Oring. Others wrap a little electrical tape on the intake.
The only way the plug could be closing is if the piston is slightly kissing it. Not good. Don't know why your clearance is so low there, cause this shouldn't be happening with a normal reach plug. If your using a plug with a longer reach than stock or you have removed material from the jug or head that could explain it, but it's still rare and needs to be fixed. Have you done a squish gap check?
