Need-help-with-quads

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So I’ve got to replace the valve guides? Would that fix the loss of power at half throttle in gear? And for some reason it revs just fine in neutral but then in gear it bogs down at half throttle

I’ve got an oem mikuni carb I just cleaned it really good all the jest are clear float is set correct and I just tuned it so I don’t think it’s carb but I mean I could be wrong

So my moto 4 is smoking white smoke and when I go to first gear and get about half throttle there’s no power and it sounds like it’s bogging

Ok I’ll make a new thread but it’s white smoke and the plug is matte black, one of my buddies told me that it’s probably piston rings

Hey so if I have another issue with the same kind of quad except just a different one do I do that here or make a new thread? Basically what happens is the thing smokes like no other, it idles and revs just fine in neutral but when I go in first and get about quarter to half throttle is sounds like it bogs but it still runs and there is massive loss of power

Ok well in that case im pretty dang sure that the issue isnt the carb because the back off issue was still happening right after i cleaned and rebuilt the carb i was mostly just wondering about float height and jet sizes but i dont know what else it could be, because the jets are clean and if thats the case with the drain and all that then i think the float height is good

Ok so before I read this the carb was already off so I messed with the float and it was ok but no matter what I did for some reason when I tilted the carb, gas would leak out the drain plug. Even though the screw was fully screwed in. Also when I tilted it gas leaked out three holes in the intake side of the carb so if it tilted then it would leak into the airbox Im just so frustrated with the carb because i already rebuilt it and i dont know what the issue is and cant figure it out

Ok yes I tried the ultrasonic cleaner and scraping as much out as I can but I couldn't get it to come off it was really stuck on there, but I just watched a video on carb tuning and I had the air/fuel mixture screw turned all the way in so that no fuel should be getting in there, and yet it still does it, would that mean I have the wrong size for one of the jets? Also the guy said something about the needle height, would that have anything to do with it?

It still does it with the speed back off, the spark plug is brand new but ive decided to sell it as is thanks for all your help sorry we couldnt figure it out but i do have one thought, when i bought it, it had been sitting for a couple years and there was like somesort of white hard calcuim buildup or something in the walls of the carb bowl and inside, do you think that has anything to do with it? keep in mind that i rebuilt it so the jets should be fine, i also just replace the petcock valve so theres nothing clogging that up also i tried coaxing up to higher rpms but that didnt work and i couldnt get it to go higher, but if i ride it for a while it tends to faster as it gets hotter

So far it’s still doing it I adjusted the carb a bit and now it doesn’t backfire as bad but it’s still not going full speed, I did find out though that once i ride it for like 10 minutes on high rpm’s I’ll get like a sudden boost of power and it’ll go faster and the speedometer will go up to 50 but other than that I’m not sure what to do there was not water in the carb so yea I’m at a loss

Sorry been busy but I had bought this quad off of Facebook marketplace and am going to flip it so it is new to me I’ve never had this kind of quad before It has just done this from the start

Ok fellas the first thing I checked is the timing and here it is. now for that F, is that the correct line because there’s also another line the first two is with the f line and the last two are the other line If this is the issue how do I adjust this?

So this happens hot and cold but when I ease off the throttle a little bit then it goes the same speed but doesn’t “cut out” quite as long There is a backfire sometimes if I ride it hard on full throttle The engine brakes don’t kick in it just loses power for about a half a second if I back off the throttle too much it obviously slows down but stops cutting out what do you mean when you asked if the exhaust is silent and the carb is gaspy?

Ok I’ll try and explain what’s happening, so I’ll hit full throttle, then once the rpm’s get up it sounds like it cuts out for half a second and then the rpm’s go back up. The thing about this is that I’ve ran it really fast before and it’s only happened like 3 time but the speedometer went past 50 so I know that it can go faster I’m just not sure why it wont

So this is normal? Also with the speedometer I can’t really tell if it’s right because I have smaller tires on the back and I don’t have the right size so it’s actually going like 30 I think RPReplay_Final1719575160.mov RPReplay_Final1719575160.mov

Ok so I found another problem, when I ride it, the speedometer wont go past 40( it goes up to 50) it almost sounds like it’s cuts out for a second and then keeps going and then cuts out, and sometimes it’ll go like 45 but most of the time it won’t go past 40

Anybody got a service manual for a 1989 Yamaha moto 4 250?

Well the screw that I was pointing to was flathead and brass so that’s why I thought it was the fuel screw, but good news I messed with it a little and was adjust those two screws and I think I got it running pretty good. I had originally bought it from Facebook marketplace and I hadn’t run in a couple years and there was a bunch of stuff missing, so thanks for your guys help I really appreciate it I’ll send a before and after picture for you guys so you can see Also sorry gw but that is definetly not the the carb on my quad haha

The screwdriver is pointing at the fuel screw but I’m wondering if I’m getting the air screw and the idle screw mixed up. If so, which screw is which on this thing?

Clarification on the throttle, reverse dies if I just barely tap the throttle, first gear only dies when I hit it hard right off the bat, if I ease into it it won’t do that

Hey how should I reset the screws cause I wanna try that and then readjust it, I know the fuel screw is 2.5 turns but what is the idle mix screw? Also I had no idea about the float height all I did when I rebuilt the carb was screw it in as far as I could (the carb was old and had a little bit of white hard build up). And now it idles fine after I messed with it but now I want to reset the screw Bcs when I go into reverse it cuts out and dies and in first gear if I slam the throttle it also cuts out

How would I go about finding that leak?

Ok so I just got time to mess with it and I had the fuel screw almost all the way in and it didn’t make any change which is weird

Ok I’ll try that then let you know