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Post Info TOPIC: Carburettor - repairing a broken carburetor - float pin post and choke


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Carburettor - repairing a broken carburetor - float pin post and choke
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Since it seems to be a common problem to break the float pin support mount on the TTR carburetors i thought i would add this simple fix to the problem.
Thanks for reading,
Cheers.
 

image1.jpg

 




  • The hole into the float pin support mount must be drilled on a slight angle so it does'nt hit the needle seat mount (pictured below)

image2.jpg
 

 

  • It is also very close to the float needle seat (shown with orange line below)



image3.jpg


  • Also a flat section ground into carby pin support mount (left side in pic) so as to have more room for the bowl and something for the tab to lock into and sit up against when screwed in...(shown below with red line)

 

 

The pic below is to shows how i bent the metal tab inwards a bit so as to have the float pin sticking out both sides not that it was absolutely nessesary it was just to make sure the pin didnt drop out. (shown in pic below with blue line)

  • Tab bent inwards to allow the float pin to stick out either side (shown with blue line below)I obviously bent the tab before screwing it to the carby.




  • This pic is to show how the pin should sit (see below)
 

 image4.jpg

 

 

 


NOTE: It wont matter if the float pin is a bit loose in the support pin hole if the float pin is sticking out both ends. Try to get it so it just grabs the float pin though.
I would advise to use a flat headed (tapered) self-taping screw to screw in the tab because i had to grind mine back a bit once tight so i could fit the bowl over.

The only real trick to it is pre-drilling the right size holes in the right place and angle.
If your not confident enough with an angle grinder i would advise to use a flat file to flatten the float pin support mount.
If using an angle grinder like i did be '''VERY''' carefull not to ruin the carby by grinding where you should'nt be.

I might add it's worked a treat for about a year now and no sign of loosening or breaking...
Also not so hard to take the pin out anymore as i drilled the float pin hole perfectly and made the other side ''float pin'' hole a slight bit bigger.
Hope this all makes sense???confuse Let me know if it doesn't or your not sure on something.




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RE: Repairing a broken carburetor
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I had a similar problem. Carb got knocked off the bench - fell and broke the post. I took it to a jeweler.

He lazer welded the post back on. looks good as new $40.



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Carburettor - repairing a broken carburetor - float pin post and choke
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At least once a month I am asked if I have a used carb for sale as the owner's float support post has been broken off trying to get the pin out.

It is such a common occurrence (done it myself!) that I have been trying to think if there is an existing tool that might push the pin through whilst holding/supporting the post. Does anyone have any ideas?

If not, what would be needed to do the job? Anyone inspired to make up a tool or suggest what it might look like?

Brian



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With all my carb problems lately, I took it to a local shop.  I've used them before and they are very well known in the trials and enduro scene and come highly recommended, and I've used them before.   Unfortunately they called me to say I need a new carb body as whilst trying to fix it, it sounds like the float pin mount has broken.   they called Yamaha and the price for a new one is £260+vat.  Obviously second hand ones are are rare as an English cricket victory.

then I spotted this post by Jarrah.  It's a same he's not been around as the image links no longer work.  Has anyone by chance got any images to go with Jarrah's post on this?

my preference is to try and get a replacement, but thought this might be worth a try.



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Sorry to hear that. There is no real pressure on the post so just give it a good de-greasing and pop the broken section of post back on over the pin with a blob of epoxy.

A lot easier than the drilling and screwing methinks.

Brian



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I have a few carbs with broken float posts awaiting repair. I am going to use the "thumb screw" technique suggested by Ronridesbikes last year and have taken the liberty of copying and summarising how it works below.

I have bought the thumb screws and am just waiting to find the time to have a try. I will report back when I do wink

Brian

First a picture to show what we are talking about:

Thumb screw repair to float post.jpg

Ron's explanation:

"It's a common thumb screw. I filed the winged sides from it. The drill and tap were $5 as a set. 

Be careful with the tap. The aluminum casting is so soft it gums up the tap threads quickly. 1/2 turn in, 1/4 turn out and remove it to clear the treads every 2 turns. Go Slow. 

I center punched the top of the post and pre-drilled with a smaller bit to be sure I stayed in the middle of the post. Make sure you drill straight down, Check it from two sides as you drill. Again, go slow. Don't drill too deep. Measure the post and put a piece of tape on the drill to set the depth. 

Don't worry about tapping all the way down. Put tape on tap as well. Let the thumb screw cut the last few threads so it sets tight. But go slow. If you feel it binding, pull out and use the tap a little more. 

You'll have to put the screw in once to mark where to drill the float hinge pin hole. Remove the thumb screw to drill the float hinge pin hole. Center punch that too. The drill likes to move around on the chrome finish. 

File the thumb screw wings to within 1/16 of an inch all around the hole so the float bowl will clear and the float it self can pivot the full radius it normally would.

Note - depending on the length of the thumb screw, you may have to cut it down. Make sure you put a nut on it before you cut it so you can clean the threads up before you mount it in the carb. "

 



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I had a go at fitting a replacement post today and my own step-by-step photo guide is here - http://www.ttr250.com/Floatpost/TTR_float_post_repair.htm

Any queries or corrections please reply on this thread!

Brian

Float installed.JPG



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brian good engineering skills

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Thanks John - much appreciated! 

I had another carb body that I had stuck on a broken post with epoxy and, although it still looked good, I thought I would do a "proper" repair whilst I had all the gear out.

Post held with epoxy.JPG

 

I was interested to see what force was needed to remove the top of the post and was surprised how well it was still held on so it's quite a good quick fix wink

Anyways up, the new support was fitted in about an hour. Would have been less if I had taken more time on filing out the hole for the pin. I went too far and the pin was loose in the hole so I had to start again with another thumbscrew. Another lesson learned biggrin

Brian



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Good post here and good suggestions. I just rebuilt a TTR 250 carb that had been sitting.........oh not good. When I got to the float pin dilemma, I slowed up and took evasive measure.
I have broke a lot of float pins 40 years ago with a little punch and toooo much enthusiasm. So I:

left the carb on my bench for a couple of day, hitting the pin area with PB Blaster penetrating oil a couple of times a day

Couple of days of prep, I used my offset nose chain materlink pliers to shove on the pin with the post as backing. WOW, way to tight but it finally slid out.

I redrilled the pin holes in both post to a slightly loose fit, and after replacing a nasty looking stock needle and seat, I turned the carb bottoms up and reset my float height with the looser float pin. All good. I have epoxied quite a few broken post over the years without issues.................that I know of, maybe 30 years later it all came apart, I don't know. For a few years its for sure a good fix.

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