![]() |
#1
| |||
| |||
![]() I have a 86 Yamaha moto4 & when you start the four wheeler it is full throttle. I have rebuilt the carb twice now. I have looked on forums and tried a few different things now and I am completely stumped. the float is working moves as it should have tried adjusting idle screw in out. bent the float arms up and down. ive adjusted the needle a few times. and I just cant seem to figure this out. Any help or suggestions would be much appreciated. Ive also checked all air flow to carb throttle cable is clean. Throttle also closes all the way. Thanks in advance for any help possible!!!! ![]() |
#2
| |||
| |||
![]() Sounds like you have an air leak in the intake system. Paw Paw |
#3
| |||
| |||
![]() I Have checked for leaks everywhere. |
#4
| |||
| |||
![]() Remember that your intake manifold seals twice on your model, against the carb. and again against the cylinder head. Its o-rings are prone to leaking after years of heat cycling the engine besides normal deterioration. I suspect, since the float valve assembly seals against the carb body by an o-ring on its o.d. & that the o-ring is bad, if so.....you can adjust the float "closed" and it will still pass fuel into the carb coming up through the emulsion tube & into the cylinder causing it to be "flooded" when that o-ring or the needle to seat is not sealing 100%! So, the float valve & its o-ring MUST be in good condition as well as all the bleed holes in the emulsion tube be clear and the o-ring between it and the extension that leads into the throttle bore, choke plunger tip must close & the rubber seal on it functional, the air bleed leading to emulsion tube also need to be clear and proper size ( I have cleaned lots of these that had dried fuel residue in them reducing their size & causing a rich condition) which can be missed in a carb clean....good luck! PS: Also your fuel petcock must be functional, it must shut off. If it does not it means its internal sealing washers are bad, this not only cause it not to stop fuel flow but often allows small bits of rubber to foul the float valve from shutting off...& again flooding. |
#5
| |||
| |||
![]() All of the seals and o rings in the carb are good the o ring from carb to manfold is good. could exaust not being tight enough cause this? also I have good compression enough to start the four wheeler but could I still be getting air from the head ? Everthing is leading too an air leak somewhere im just not finding where this air is coming from ---------- Post added at 03:19 PM ---------- Previous post was at 03:04 PM ---------- does anyone know how many pounds/psi I should be getting compression wise? |
#6
| ||||
| ||||
![]() Not sure on compression but thats not why it's revving up. Are you sure the carb slide isnt sticking in the carb? |
#7
| |||
| |||
![]() yes I am very sure the slide is not sticking. slide all the way down as soon as it starts it is full throttle tried lifting the four and putting it in gear when it starts and still full throttle |
#8
| |||
| |||
![]() Oops I misread your initial statement, I thought you said it must be FULL throttle to start. Anyways, take the slide off the cable & manually slide it up and down the bore making sure that it does so freely and has good engagement with the alignment pin. Make sure that the pin is holding the cutaway on the lower part of the slide towards the air filter & that with the idle screw out that the slide closes fully at the engine side of carb. Also check that the needle is straight and not dragging on the emulsion tube of the carb & holding the slide open, the slide does not have to be open very far to act like it is full open when its in neutral-yes I know you stated the slide is not open but it really sounds like it. Make sure the is no excess wear on the slide and you cannot see light around the sides of the slide, that would have to be quite worn but worth checking. |
![]() |
|
Thread Tools | |
|
![]() | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
1986 Yamaha Moto4 smokes on deceleration | two smokes | ATV/UTV - Yamaha | 20 | 04-03-2014 02:23 PM |
86 yamaha 225 moto4 | gmcsonomaguy | ATV/UTV - Yamaha | 5 | 10-12-2011 06:29 AM |
cr 250 1986 clutch problems | carlcr2501986 | 2-Stroke Dirt Bikes - Honda | 2 | 01-16-2011 08:15 AM |
1986 CR 125 Problems | CR125 | 2-Stroke Dirt Bikes - Honda | 10 | 05-24-2006 01:55 AM |
New CT 680 kit...Carburator problems...HELP | raptor fan | ATV/UTV - Yamaha | 1 | 12-30-2003 12:51 AM |