"D" Motor Carb Adapter

[VICTOR MONZ]

I am need of the rubber adapter for a 125 cc "D" cylinder that connects the 30 mm Mikuni to the cylinder....mine leaks a bit of air, not good.

Any assistance would greatly appreciated.

Victor

[rob w]

Victor,
Here's an option. In Sudco parts (on line), there's a "rubber mounting Flange" in the "Intake" category.
Part # 002-053 has a mounting hole spacing of 60mm, you'll need to enlongate the holes to apx. 68mm ctr. to ctr.
That part also has a 40mm spigot opening. Measure your carbs spigot to see if that will work.
I'm not positve about the 4mm step down needed to seal where the manifold meets the cylinder.
That's one direction.
Bob

[brian kirby]

Sudco (they are Mikuni made manifolds) also has a manifold with 60mm bolt offset like the one Bob posted, but the spigot size (ID of manifold) is 35mm which might fit your carb better, the part # is 002-050. You will still have to elongate the holes though.

Brian

'73 Berkshire Team  d-Con
//www.d-conproducts.com America's #1 Rodent Control Brand

[john durrill]

Victor,
Here are 2 tables for manifolds that Sudco sells. See if one can be adapted or one has the right dimensions for the D cylinder.
 Let me know if one will work and i can put it in the Library.



On the Amal adapters the stud center is 2" I used one of the 2" one's to adapted a new big body 26 mm Mikuni to a Gem Reed on a 125 Hodaka for a friend. They were expensive but it did let us adapt from the old equipment to the new run Mikunis .
 John D.

[VICTOR MONZ]

Thanks gentlemen.  I do have a SUDCO book and after checking my "old" adapter found some modification would be necessary, it appears that is the concensus.

I got lucky this morning "rooting" around in my stash of parts and found an original one that isn't too bad and "gooped" it up a bit and stuffed in on....will let you all know, once it drys.

I will contact SUDCO tomorrow and see about getting a spare to modify and have on hand.

Thanks again.

Victor

[firstturn]

Victor,
  All you have to do is buy one of their manifolds and use a frontend seal for the spacer.  Use the size seal that matches the size manifold you are using and use a gas resistant sealer and you are done.  Do a leak test and go racing.

Ron Carbaugh

[VICTOR MONZ]

Thanks Ron....I forgot, I think we had this discussion a year or 2 ago.  The fork seal works great to seal at the motor with a washer or 2.

I appreciate all the input.

I ran the bike last night and have a Mikuni question...the bike runs great till 3/4 to full then she seems like it 'flattens" out and begins to sputter.  I have a 230 main jet in it, plug is tan which leads me to believe I have the jetting right....would the timing have something to do with it??

Looking for top end help !

Victor

[firstturn]

Victor,
  What is the timing now and what type of ignition are you using now?

Ron Carbaugh

[VICTOR MONZ]

Ron:

I put a brand new PVL in and it is timed at 2.8 mm  BTDC and has a 30 mm Mikuni.

Thanks for the assistance.

Victor

[firstturn]

Victor,
  2.8 sounds fine, but I would double check the timing.  Also, be sure your slide on the carburetor is opening all the way up and that your choke is all the way closed.  Next I would be sure you grounding is OK.  If you have installed the engine in a new frame that has been painted besure your engine is grounding to the frame.  Just do the easy stuff like disconnecting the kill switch and make sure you don't have a shop rag floating around in the air box or that you filter doesn't have too much oil.
  Sorry it took a while to get back with as someone used the side of my truck as a bumper car....everyone is OK and they can repair trucks.

Ron Carbaugh

[454MRW]

The 250 that I rode in the 40th parade last weekend exhibits similar symptoms. I removed the 36mm Bing from another 76 MC5 bike which the piston showed no signs of detonation or scoring, so I was relatively sure that the jetting was fairly close. I am running a 1981 torque pipe on this particular bike which may contribute to a slightly leaner condition. I cleaned the carb thoroughly and had slight leaking from a high float and once reset, it ran great except for over 2/3 throttle, which it flattens out and slows down, but with the choke 1/2 on, it runs great and revs out very clean. It may be a jetting problem even with a good plug reading, but I expect to find a fuel restriction in the needle or float setting or possibly a resriction in fuel flow at the petcocks. The bike surged at slow speeds in the parade, so there may be a vacuum leak contributing to the problem. Just a thought. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[VICTOR MONZ]

Dear POGERS:

I put a 28 mm Bing, after I rebuilt it at 3:30 am this morning and it ran nice and fits just right in the stock adapter to the "D" cylinder.  

I couldn't "wring" it out till I got home from work, the neighbors just don't understand motorcycle mindsets at 4:00 am, and just got off it.  It went all the way through the throttle without the difficulties I was having with the Mikuni at the top end....HMMMM.

Looks like the Bing is headed to Perris MX on Sunday.

We'll see..I sure appreciate all the input from you all.

I will report the results, hoefully good ones.

Thanks again.

Victor:D

[brian kirby]

Victor, your symptoms on the Mikuni sound like the choke plunger may be leaking. I have see new ones leak from a tear or crease on the flat rubber area the seals off the fuel port. It will start as a slight miss on the top and start to get progressively worse. I had one do that on a Can-Am, I put a new plunger in it and it works like it should.

Brian

'73 Berkshire Team  d-Con
//www.d-conproducts.com America's #1 Rodent Control Brand

[VICTOR MONZ]

Ron and Brian:

I am leaning towards you're choke idea....it is a brand new carb, however I had to grind the lever a bit to clear the fins and it subsequently broke.  I took it in and out a few times and may have damaged it.  I will look into it and replace it with a new one I have from another carb.

Thanks.

Victor

[firstturn]

Victor,
  I hope this is your problem.  It is great when we can exchange ideas.  

"Also, be sure your slide on the carburetor is opening all the way up and that your choke is all the way closed."

Even a blind hog finds an acorn......be careful out there and have fun.

Ron Carbaugh