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The TTR250 FAQ web pages -> TTR250 -> Carb stuff -> Adjusting the fuel level in the carb bowl - float height
Post Info TOPIC: Adjusting the fuel level in the carb bowl - float height
Allweatherbiker


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Float height please
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Hi I need to know the float height of a 4GY in mm from the base of carb....I looked in a manual and it says I need to order a tube with measurements on it to check/adjust the float. Just wanted to know if anyone knows the height so I don't have to spend money & wait ages for the Yamaha part for this job.

Many thanks

Elt



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Cubber


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I think this is what you must be after.     confuse

Image2.jpg

It is from the Service Manual of the TTR.

Martyn



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Allweatherbiker


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wow thanks for that.....I must have a different manual to you. Top man :)

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burton500


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I take it you measure the float height with the carb inverted, and its the distance from the edge of the carb body to the top of the float? 



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TTRfan


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Adjusting the fuel level in the carb bowl - float height
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Adjusting float level.jpg

The page above came from a blue TTR manual and it's different to the instructions in the older TTRs' manual which, in step 4 (actually it's instruction 5 in the older manual), adds "and warm up the engine for several minutes"

I am missing something here - why warm the engine up on the older TTRs?

I am about to check/adjust the float level on a carb that is off the bike so what allowance do I need to make - if any confuse

Brian



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TT-R250M


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RE: Adjusting the fuel level in the carb bowl
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I am not sure why it says that but just disregard it. As long as the fuel level is 7.5-9.5mm under the float chamber mating surface you will have no trouble.

You can even just go off the line off the side of the float. If it blocked the fuel off when the float is level, it is good enough.

Jarrah



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TT-R250M


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I would hazard a guess that the Open Enduro models have a slightly different nozzle and main jet washer (AKA splash cover). They may have experienced an airlock inside the main jet washer or main nozzle/jet so they added that? If so, surely tapping with the blunt end of a screwdriver would fix that. Other than that, I cannot see any difference between the two models or reason to warm the engine up.

Jarrah.



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Craiginuk


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RE: Float height please
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Hi, sorry to resurrect an old thread. Would this measurement apply to 2005 model? I get about 23mm from bottom of float to mating surface with carb inverted. Carb was leaking through overflow so suspect float level might be out. Could not check wth tube as it was leaking constantly.

Cheers
Craig

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TTRfan


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Hi there.

It seems unlikely that the float height would have changed by itself. I would suspect a problem with the float valve. Either it's worn or has a bit of dirt trapped under it preventing it closing fully.

Brian



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Craiginuk


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Thanks Brian. Previous owner had carb cleaned out by someone. Just not 100% sure he knew what he was doing as it has never run properly. The float tang seems totally flat. I.e. No angle on it at all. I will reassemble with the new valve and then check float level with tube before I reasemble everything. Was just wondering if i could check by measuring first.

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UCttr250


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Adjusting the fuel level in the carb bowl - float height
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Hello all!

First I'd like to thank all those that have created or contributed to the stickys on this forum as they've allowed me to go post-less since becoming a member in 2006 haha. 

My question: does anyone have some tips or tricks on tweaking the brass piece that regulates the float valve needle?

California 2006 TTR250

I had my carb apart, cleaned it, reassembled it and got it in the bike. I then turned the pet**** over and after a bit fuel began rushing out of the drain hose that comes off of the bottom right side of the carb. 

I took the carb out. stripped the bottom half down and re-cleaned. I sprayed air through the fuel entry point (where the fuel tank connects) and felt it coming out where the float needle is . I Then lifted the float so that it would close the valve and it did close it. I didn't feel air being blown through anymore.

So I'm assuming it has something to do with my float level? I haven't put it back in for another test after this cleaning session. I think what I will do before i put it back in the bike is connect it to my gas tank and wait for the carb to fill up to see if it overflows again. 

Any and all help is appreciated!



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2006 Yamaha TTR 250

2001 Honda RC51

2006 Harley Davidson Super Glide
UCttr250


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Disregard my earlier post! 

I found the answer above disbelief

Also my off-the-bike carb test worked. I ran fuel through the inlet from the detached tank and float valve/pin cut fuel entry. I refitted the carb in the bike and the fuel leak stopped biggrin



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2001 Honda RC51

2006 Harley Davidson Super Glide
TTRfan


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I have led a charmed life up until now as far as float height problems are concerned. I fitted a carb I have rebuilt to my TTR to test it out. Not long before I heard the ominous drip of petrol from the overflow cry

So off with the petrol tank and airbox and carb removed for adjustment.

I put the tank on the bench and the carb on a stool with a container to catch waste fuel underneath it.

I was lucky to find a length of clear plastic that fitted perfectly over the overflow tube at the bottom of the float bowl.

I found it to be an awkward job - definitely not one of my favourites! It took a few attempts to get the fuel level between 7.5 and 9.5mm but the job is done and I can get the carb back on tomorrow.

Float level check1.jpg

 

Fuel level sits just about perfectly between the two marks biggrin 

Float level check2.jpg

 



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TTRfan


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Well - that had to be one of the most difficult and long-winded diagnostic jobs on the TTR I have experienced no

I fitted the rebuilt carb and it road tested great but blubbered on tickover indicating a rich mixture at idle.

After a zillion attempts at re-setting the float level, swapping pilot jets, taking time out to understand how the pilot circuit works, swapping out the pilot screw, etc., I discovered I should have been looking elsewhere for the problem disbelief

I tried to think what could cause the over-rich running at tick-over. If float height, air leak through pilot screw, and too-large pilot jet were discounted what was left?

It was like the choke wasn't completely shutting off...... and, yes, there you have it!

The rubber seal on the end of the choke looked good but I was suspicious it wasn't seating. To check it, I wrapped a bit of Blutack around the end of the choke and pushed it against its seat in the carb. The pattern on it was not circular and indicated a problem with its seat in the carb body.

My eyesight isn't great so I took some photos which showed that the seat was damaged and only about a third of it was left smooth and intact:

Choke seat damaged.jpg

 

At some point in its history the choke had seized into the carb body and the usual remedy applied - drilling in from the outside and tapping the choke out with a small punch. It seems highly likely that during this process the choke seat sustained this damage. Shame coz the carb body is now scrap cry

I had another carb body that was good and moved all the parts across. 

This is what the choke seat should look like!

Choke seat undamaged.jpg

Fortunately the float height checked out perfectly so the next job is to fit and road test it!

Brian

 



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