I'm interested in getting opinions from trusted POG members. I have my second JP for restoration. The first one was a '72 that was kept stone stock, complete with Amal carb, and turned out pretty good. The second one is a '73 that has a reed valve installed with a Mikuni carb. I haven't looked at the porting and piston skirt yet to see if they have been modified. I tend to want to return it to stock with a Bing carb, but would be interested in your thoughts. Thanks in advance for your input.
Nelson Lingle
The reed helps the bottomend power of the pipey Jackpiner in my opinion. The piston and porting had to be modified for the reed to work right.
Larry P
Are you going to ride it? If so, what kind of riding?
I found my '75 was pretty good everywhere, stock, but then I never rode it in a muddy, tight Illinois enduro either. But I did use it for MX, desert and enduros in large rocks in Arizona. I found it had pretty good bottom-end power for a small-bore.
John
Nelson,
My thoughts are - whether it's for show, or go - it would be quite okay to leave the reeds and Mikuni on the bike. Those parts may not be stock, but it was a common modification, correct for that period.
One of the issues I have is - where do you get replacement reed petals if they're bad ?
Bob W
Bob,
Boysen Reeds makes replacements that fit the GEM Reed setup for the 250/400, can't recall but assume the 175 GEM was smaller (?) and that Boysen has one for that too. I can look up the part number for the 250 reed I run on a couple bikes if it helps.
Mac
Unfortunately, the reed setup that I have does not seem to be a GEM system. The GEMs that I am familiar with is an aluminum casting with the name cast in. This one is more of a billet design with no name. The reeds are metal rather than fiber. If I stay with the reed and Mikuni arrangement, are there suggestions as to where to look for a carb-to-airbox boot to adapt to the larger inlet of the Mikuni and the shorter distance resulting from the reed block? Thanks again.
Nelson Lingle
A good "lightly used" Bing for the JP are getting harder to find, intact.
Someone had put some effort into fitting the reeds and Mikuni on your JP, at one time. If it works well and starts good, I'd stay with the Mikuni.
Personally, I'd be getting rid of that metered leak controller :D
(Amal)
2c
Raymond
Down East Pentons
Raymond,
Thanks for the opinion and recommendation. Any suggestions on where to find a carb/airbox boot?
Nelson
Hi Nelson, I think awhile back there was a string (postings) on mounting/ running the Mikuni carbs on the JP. Im hoping someone will chime in here, and have some insight on solving your particular situation.
I know its been said and done, try a search on this website any way.
Raymond
Down East Pentons