Hairline cracks on phm40

Ducless · Post by **Ducless** » Fri Mar 18, 2011 8:05 pm

i started inspecting the phm 40's on my newly aquired darmah. the PO tried to have the bike brought back to life about 5 years ago but the dealer he took it to kept it for the winter and come spring told him that their mechanics could not work on it and that he should pick it up. anyway, the dealer did remove the carbs and partially disassemble them.

so today i started to clean them and i noticed in the throat of one of the phm's that there are a few small hairline cracks on the inside of the throat coming from the bottom of the relief cuts that get compressed by the clamp. none of the cracks can be seen on the outside and they are at most only 1/8" to 3/16" long. they will be completely covered by the plastic sleeve. the cracks were only on three out of the four relief cuts and one of the cuts only had one crack. so there is a total of five cracks.

so my question is, should i be concerned about these cracks or is this normal? also, if i run the individual clamp on air filter pods, should there be a small bellmouth screwed onto the back of the carb that the air filter goes over or can the airfilter simply mount right onto the threads?
thanks
dave

Post by **BevHevSteve** » Sun Mar 20, 2011 2:31 pm

Hi, yes you should be concerned about these cracks. They were caused by your idiot dealer doing a wiggle wobble to pull that carb off the intake manifold and not simply twisting it off as it should be done.

It can be fixed though. Simply drill out 1/16" holes at the end of each crack, this will keep the crack from continuing to grow longer, then fill the holes with JB Weld.

20 years ago, the thing to do was to shorten up your original velocity stacks, then stick them inside a K&N air filter. Now, K&N have changed the design of the INSIDE of their filters so they are smoothe and have a lip much like what a velocity stack would accomplish. So, we mount the air filters directly onto the threads on the carbies - no problem.

Ducless · Post by **Ducless** » Sun Mar 20, 2011 3:29 pm

thanks, sounds like a quick and easy fix.

Post by **BevHevSteve** » Sun Mar 20, 2011 3:32 pm

yep - didn't say so but the plastic sleeve should be removed first, then drill and repair.