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Hi,

I hope you guys are still brave enough to ride with the current weather.

While during some winter prep on my 04 T100 I noticed that the fuel Bowl thread was completely chewed up and the screw wont hold up. My plan is to go down the helicoil route to fix the thread. Has anyone experienced similar issues with the carb's bowl screws? I don't own a bolt gauge nor a caliper and wondered if a kind soul would happen to know the screw size of number 15 below?






Thanks in advance and happy riding.
 

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M4 x 0.7mm x 16mm long rings a bell, I could be wrong but I think that is the size of socket head cap screw I put on mine after rounding out the JIC screw heads. This is on my dirt bike carb (Keihin PWK36).
 

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Let us know how it goes with the helicoil. You don't have much metal mass to work with.
 

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Here is the info. I have on the screws from the notes. Note - If I read correctly and understand that you actually have stripped thread in the carb body [ female side ] and there are no salvageable threads left, then as Mr. Balto stated, there is very little material area in the body to do an insert. I would recommend if that is the case look into whatever the next metric and American standard size is to just tap out one size over the M4. It would make that one screw a bastard compared to the other 3 but that is what I would do.
Here is the info.

Carb bowl screws: Size is M4. Commercial kits come with:
8x M4 x 8mm long for the top caps
8x M4 x 14mm long for the carb bowls.

It's best to substitute two of the 14mm ones for a couple of M4 x 16mm long for use on the two rear screws of the left carb. This is because those also hold the idle adjuster bracket and as this adds thickness there's very little left to screw on to the carb body and they can strip easily. So the revised list becomes:

6x M4 x 14mm long for the carb bowls
2x M4 x 16mm long for rear left carb bowl screws.

Extra info.
8x M4 x 8mm long for the top caps - [TOP CARB CAPS]
 

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I wouldn't try helicoiling it as the external thread of a M4 helicoil is too big, about 6mm.
best option is next screw size up. go to a bolt and fastener specialist, or even ebay.

M4 and all screw threads never have the major diameter the same as the nominal diemater, but are slightly under. 4.00 mm in this case would be 3.98mm and could be down to 3.85mm thread diameter, ie 0.152". so your stripped hole would be about that size.

a 7/32" screw has a major diameter of 4.19mm (0.165") and may screw into the soft carb alloy forming a thread without the need for re-tapping.

and seeing that you are England, a #2BA, even though they are obsolete, should be easily available which has a major diameter of 4.7mm (0.185") and may do the job

M5 range from 4.98 to 4.83mm, but maybe too big.

and for the float bowls I'm sure I used 16mm length s/s capscrews for all instead of 14mm long as mentioned by Back2-2
 

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I wouldn't try helicoiling it as the external thread of a M4 helicoil is too big, about 6mm.
best option is next screw size up. go to a bolt and fastener specialist, or even ebay.

M4 and all screw threads never have the major diameter the same as the nominal diemater, but are slightly under. 4.00 mm in this case would be 3.98mm and could be down to 3.85mm thread diameter, ie 0.152". so your stripped hole would be about that size.

a 7/32" screw has a major diameter of 4.19mm (0.165") and may screw into the soft carb alloy forming a thread without the need for re-tapping.

and seeing that you are England, a #2BA, even though they are obsolete, should be easily available which has a major diameter of 4.7mm (0.185") and may do the job

M5 range from 4.98 to 4.83mm, but maybe too big.

and for the float bowls I'm sure I used 16mm length s/s capscrews for all instead of 14mm long as mentioned by Back2-2
That's great advice. Anyone having an issue with carb screws should read this.
 
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