Penton Owners Group

General Discussion => Penton Talk => Topic started by: Denis Jeffries on March 13, 2009, 01:08:38 PM

Title: jackpiner mikuni switch
Post by: Denis Jeffries on March 13, 2009, 01:08:38 PM
I would like to trade out the bing on my jackpiner to a 34mm mukini. Would this be to large and what type of problems will I run into.
 Thanks for the help
 DJ
Title: jackpiner mikuni switch
Post by: Dwight Rudder on March 14, 2009, 12:35:29 AM
The bike came with a 30mm.  I wouldn't go bigger than a 32mm. Many people go with too big a carb and gain top end at the expense of low end.  I suggest keeping your low end torque.
IMO,
Dwight
Title: jackpiner mikuni switch
Post by: Denis Jeffries on March 16, 2009, 08:46:46 AM
Dwight,

 Thanks for the help. I'll try and find a 30mm or a 32mm. Thanks again
 DJ
Title: jackpiner mikuni switch
Post by: brian kirby on March 16, 2009, 09:57:54 AM
Dwight is correct, typically you only need to go up 2mm when doing a Mikuni swap and as he said it had a 30mm Bing stock so 32mm is the size you want.

Brian

'73 Berkshire
Title: jackpiner mikuni switch
Post by: VICTOR MONZ on March 16, 2009, 03:10:14 PM
DJ.

I'll take that "old" Bing off your hands, once you've went Japanese.

E-mail me offline if you want me to dispose of it for you.:D

Victor
Title: jackpiner mikuni switch
Post by: Denis Jeffries on March 17, 2009, 11:23:36 AM
Quotequote:Originally posted by brian kirby

Dwight is correct, typically you only need to go up 2mm when doing a Mikuni swap and as he said it had a 30mm Bing stock so 32mm is the size you want.

Brian

'73 Berkshire
Title: jackpiner mikuni switch
Post by: Denis Jeffries on March 17, 2009, 11:26:12 AM
Brian,

 Thanks for the info. I've found a 30mm and a 32mm.

 DJ
Title: jackpiner mikuni switch
Post by: clayman on March 18, 2009, 09:41:30 PM
I am having carburetor issues with my 1973 175 Jackpiner. After a thorough cleaning it runs momentarily but then runs out of gas. This is a goofy question: is the handlebar-mounted Magura lever intended to be a choke? It ran great with it in the "open" position but barely runs with it off. Are rebuild kits available for the Bing (Model 84)?

Or, should I avoid all of the headaches and put a 32mm Mikuni on it? If so, I won't be able to mount the carb to the airbox boot, will I? Does anyone have the jetting specs for the Mikuni or an idea if I can get one already set up?

Thanks so much,

Clay
Title: jackpiner mikuni switch
Post by: G Ellis on March 18, 2009, 11:43:45 PM
Clay the lever on the handle bar is a choke. On position is when the cable has nothing showing. Off position is when the cable slack is taken up. When riding I like to take a piece of tube and tie it to the crossbar in a loop. Hooking it to the choke so it does not slide open. Hope this will help. Gary
Title: jackpiner mikuni switch
Post by: Steve Minor on March 19, 2009, 07:41:37 AM
Gary is right about the inner tube trick...it works great. Here's another trick....If you come up on a long, high speed section like pavement, apply the choke slowly (while riding) util the motor starts to sputter, then back if off slightly. You may have to fiddle with it some. This will help prevent the piston from seizing. Just remember to reset the lever when you get back into the tight stuff...

Steve Minor
Wilmington, NC
Title: jackpiner mikuni switch
Post by: tomale on March 21, 2009, 05:11:22 PM
clay, Are you sure that the problem is not petcock? Or maybe the float is sticking closed. but I am also wondering about the condition of carb, when is the last time that the slide or the needle jet/jet needle been replaced. A conversation with Bing Int. recomended to me that the needle jet and jet needle needs to be replaced once a year. and if the slide is worn it needs to be replaced as well...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)
72'sixday (project bike)
Title: jackpiner mikuni switch
Post by: clayman on March 22, 2009, 11:02:31 AM
Hi Thom,

I loaded the JP 175 in the Toyota and made a road trip yesterday, meeting Larry Good in Roseburg where he pulled the carb and noticed that the float level was off and a couple other issues, so thanks to LG for diagnosing the Penton. He also hooked up me and our buddy John Raliegh with a lot of good parts....Thanks LG!:)

Hope you are doing well Thom and I'll see you at the next Woodland....please don't forget the sidepanel, I sure need it for the 125 Six-Day project. Have a good weekend.

Clay
Title: jackpiner mikuni switch
Post by: tomale on March 23, 2009, 12:05:08 AM
glad to hear that you go it worked out... I sent you a note about the sidecover..

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)
72'sixday (project bike)
Title: jackpiner mikuni switch
Post by: clayman on March 23, 2009, 08:59:00 AM
Thom,

It looks like I'm back to where I started, though, on the 175.

It fired right up and sat there and idled for 6, maybe 7 minutes and when I went to ride it, I got about 5 feet and it sputtered to a stop and wouldn't start again. I changed the plug several times and gave it a shot of starting fluid, but it's a no-go. Well, maybe LG knows what it is.

Got your email, thanks....see you at Woodland.

Have a great week!

Clay
Title: jackpiner mikuni switch
Post by: gooddirt on March 24, 2009, 08:36:21 PM
Did you take the bath towel out of the air box?[:0] And take off the SuperTrap end cap and start it ! It needs at least 2 to 3inchs of dics not the 1/4 inch you have:(. The spark I think looked a little weak  but it was raining pretty hard and my glasses fogged .[8D]
Title: jackpiner mikuni switch
Post by: john durrill on March 24, 2009, 09:13:17 PM
Dennis,
 6 to 8 Trapp disc's on a stock 175 cylinder and pipe should equal the stock end cap. It has on the 75 175 we have. And Larry may have hit the nail on the head mentioning spark. If you can, change out the ignition with someone for a test.
 It sounds a lot like ignition from what you have said. We had 1 spare on the shelf for every model. If things didn't make sense in about 20 mins. back in the day we would swap the whole thing out. Most times it did solve the problem.
John D.
Title: jackpiner mikuni switch
Post by: clayman on March 24, 2009, 09:43:53 PM
Hi John,

It's me, Clay, with the other 175 carb woes......good call on the ignition. LG (2009 Penton King of the Northwest)said the spark looked weak, but Bill the former Penton King (of the '70s) says you can't kick it fast enough with a Motoplat to see it spark....it was really rainy and hard to see anything. We were all about to shoot ourselves from the depressing rain and cold that never seems to stop here in Oregon, anyway.

Hopefully, LG will get that 125 done for me and I can give the 175 a boot out the door:D

Clay