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How to repair stripped carb float bowl threads


Ever backed out a stuck screw on you carb and brought the threads out with the screw or crossed threaded the fine threads on your costly carb and think its trashed well think again, here is a simple fix to get you going again within under an hour.

I'm about to show you how to stripped threads on a flat fcr carb and these procedures follow (should be similar on other models)

first you need to go to a local auto-parts store or hardware store and get a helicoil kit for the stock bolt size m4 x 0.7 (standard on fcr 37 flat side carb) others models may be different) mine was purchased at koi auto parts for around $30.00 but we got my dads discount actual price is closer to $55.00 the helicoil kit comes with 12 helicoils and the proper tap tool, you also have to purchase a 11/64 drill bit to oversize the the hole and drill out the remaining threads so you can inserts the helicoil.

Get a clean work space.


Now gather your tools.

Assuming your float bowl is already off due to the stripped threads in the hole if not remove now.


Gather your Helicoil kit or similar kit (Helicoil brand part #5546-4)


11/64 drill bit drill and some fresh screws to put in the new inserts anti seize torque wrench i used a 1/4 inch pound wrench


and lastly some lube for the threads when you drill them.

Step One

inspect the carb (Im pointing to my stripped hole below)


now clean out the the loose thread debris with a fine pick or something similar. now get your drill and insert the drill bit and start drilling out the damaged threads (i replaced all mine to be safe but the bad one was really the one by the fuel inlet this is a tricky one because you cant drill all the way through like the others so you have to measure the depth and set the depth with a bit stop so you dont go too far and go into the fuel inlet cavity. * TIP (securing in a vice makes this whole process easier)


(showing the bit stop)


Step Two

get out your tap and make the new threads for the Helicoils to thread into.

once you do this get the Helicoil insert tool and thread them in to the hole you tapped thread them a 1/4 to 1/2 below the edge of the surface. (except the back ones that are used to line up the bowl go ahead and insert these into they are flush enough for the bowl to flushly seal the surface) lastly you can break the tang on the Helicoils but its not needed if you chose not too.

(showing the tapping)


Lastly take your carb and blow through and clean with compressed air to get any metal shavings and insert your new screws into the bowl just as you did before and reassemble but this time use some anti seize so this does not happen again.Now torque them down properly i used a 1/4 inch pound wrench.

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