Mrcrowley
New member
I have a feeling this will be aon going post till I get my carbs back together . Anyways on the float is the square spring on float valve supposed to go over the float adjustment tab or under? SOmeone said Pilot screw from being tightened 1 and 1/2 turns out but the manual say's 2 turns out which should I do? Do I have reed valves in my sled and should I replace them while I have carbs off? I have need float valves and seats and all new orings I did a enitail cleaning till I found out the Pilots needles orings on two carbs were disintegrated . Do I really need to replace the Orings in the Chock assembly ? And leveling the float if it is inline with to where the float bowl seats that is correct isnt it?
Thanks for any help you guys can offer .
( I would go so far as to ask for someone to do facetime with me to guild me along this is the first time I have had to do a carb on a larger machine like this so offer stands)
Sincerly JIm
(Psss...I am trying to get this old boy running for this weekend family is coming up and I would love to give granddaughter a ride on the tried and true machine .... )
Thanks for any help you guys can offer .
( I would go so far as to ask for someone to do facetime with me to guild me along this is the first time I have had to do a carb on a larger machine like this so offer stands)
Sincerly JIm
(Psss...I am trying to get this old boy running for this weekend family is coming up and I would love to give granddaughter a ride on the tried and true machine .... )
JohnnyG383
Member
Mrcrowley
New member
First link is not working I have second link but hard to see if needle valve hooks over the tab or under
The spring goes above the tab ("pulling" the needle valve down when the float drops). Setting the float height level with the float bowl flange should get you close enough.
Mrcrowley
New member
Ok got carbs back on but after few minutes it starts to backfire if I give it gas and then let off runs better with choke on for few minutes then starts to whine down and backfires really lean also any ideas and I am hoping it is not a piston ?
Hammer Down
Member
Pilot jets probably.
JohnnyG383
Member
Mrcrowley
New member
Ok tried to bypass TORS nothing I am going to get new plugs tomorrow what do you think the steps I should take to trouble shoot this problem ?
JohnnyG383
Member
when you had the carbs off did you inspect the reeds? Also the carb boots are they cracked at all when it's running I spray brake cleaner or carb clean around the carb boot area to check for vacuum leaks
Mrcrowley
New member
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I am going to readjust pilots if no change off the carbs come I'll inspect boots on engine and reeds I'll also make sure my floats are correct height . Then I'll pray to god I get my old boy running well again (sigh)
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Mrcrowley
New member
ok I readjusted pilots to 1 1/2 turns no back fire but when i give it gas it starts to die till it stalls could mt floats bowls not be getting enough fuel? mt understanding it the float bowl supplies gas when you gun it?
If you want to better understand how it works there are some good pics on the web and even some links on here. Just look for Mikuni TM flatside carbs. There is a bit of detail to understand so I won't try to go through it all in a post. Olav Aaen's carb book is great too.
The float bowls simply keep the jets submerged in fuel such that when the pressure is right they will allow a metered amount of fuel to be pulled in that circuit. Obviously the needles in the main jet affect it's metering rate depending on throttle height (position). The fuel height needs to be kept within a certain level for the fuel circuits to work properly. This is adjust with the tang on the needle valve (different needle).
The pilot circuit has 2 orifices in the venturi (1 under the slide and another behind the slide). Flow in the front one (under the slide) reverses direction when the slide is raised beyond a certain height. Air goes in the front one at idle but reverses direction above idle and fuel comes out. Fuel always comes out the rear one behind the slide. This is how Mikuni was able to avoid having an overly rich idle mixture (like other carbs of the time) or using an accelerator pump. Basically when you hit the throttle from idle it needs more fuel then a single pilot circuit can supply until it gets on the main jet.
My advice is to study the Mikuni charts that describe which components affect which throttle range and dig into those. This is of course assuming that the reeds, intake, exhaust, and engine itself are all good.
I didn't read the whole thread but I suspect your reeds.
The float bowls simply keep the jets submerged in fuel such that when the pressure is right they will allow a metered amount of fuel to be pulled in that circuit. Obviously the needles in the main jet affect it's metering rate depending on throttle height (position). The fuel height needs to be kept within a certain level for the fuel circuits to work properly. This is adjust with the tang on the needle valve (different needle).
The pilot circuit has 2 orifices in the venturi (1 under the slide and another behind the slide). Flow in the front one (under the slide) reverses direction when the slide is raised beyond a certain height. Air goes in the front one at idle but reverses direction above idle and fuel comes out. Fuel always comes out the rear one behind the slide. This is how Mikuni was able to avoid having an overly rich idle mixture (like other carbs of the time) or using an accelerator pump. Basically when you hit the throttle from idle it needs more fuel then a single pilot circuit can supply until it gets on the main jet.
My advice is to study the Mikuni charts that describe which components affect which throttle range and dig into those. This is of course assuming that the reeds, intake, exhaust, and engine itself are all good.
I didn't read the whole thread but I suspect your reeds.