sunny wrote on 12/31/69 at 16:00:08:let us revisit the jet size necessary for my bike, if you don't mind.
my friend (detail oriented type

)is very leary of shadetree type mechanics so wants to know if the size recommendation for my bike/pipe combo is backed up with dyno runs before he helps me replace the jet. you all recommended a #152.5...
my bike:
all stock save for the pipe, a jardine, with blueing.
i did the airscrew adjustment two months ago.
yeah the backfiring is back but in an intermittant way, and it doesn't bother me.
damaging the pipe does bother me.
Well, in this case, your friend will be very leary of me, because I am a 100% shade tree mechanic. I've been meaning to buy a dyno and set it up in the basement, but funds were tight so I opted to buy every single jet size from 147.5 to 160 and go out under the shade tree.
That means that without anything more than experience and trial and error I found a combination that works. That may not be good enough for your friend, so the gamble is all yours. You take my word for it, spend $4 on the jet and and he does 30 minutes labor.
Besides, it's already too late if your Jardine is blued, but you can still fix the intermittent backfire.
Is your friend even a shade tree mechanic? 8)