Mikuni for a JD?

[BoschZEV]

A good friend successfully competed in the most recent Cannonball using his 1923 JD, but now he would like to replace its carburetor with something that is more user friendly. Has anyone transplanted a Mikuni onto their JD and, if so, can you give me the details of what is involved?

Clearly a manifold has to be made, but what model Mikuni, choke size, jetting, etc. are required? He isn't interested in authenticity so he really does want a modern Mikuni rather than a replacement Schebler, Tillotson, Zenith, or whatever.

[T. Cotten]

BoschZEV!

Please tell your friend that no modern carburetor is more friendly than a Schebler DLX or Linkert, if all is in order!
(Would you rather adjust with knobs going down the road, or stop and bleed everything to trial-and-error jets, needle settings, etc.?)

And he would need only to refurbish the original manifold, not "re-invent the wheel".

Please ask him if he really wants to paint a moustache on the Mona Lisa.

....Cotten
PS: If I already serviced his carb and manifold, reassure him that he won't pay twice if issues arise.

[BoschZEV]

And he would need only to refurbish the original manifold, not "re-invent the wheel".

He doesn't want to reinvent the wheel. He wants the specifications from someone else who already reinvented it.

Trust me, he really, truly, honestly wants the information on adapting a Mikuni, not adjusting an XYZ. A separate thread could be started giving all the reasons and opinions why someone should stick with XYZ, but here the question is, what does my friend need to know to switch to Mikuni.

[Shaky Jake]

I've never invented that wheel, and it's probably not something I personally would do. But I will offer that I've used Mikuni carbs on various dirt bikes and a British twin from the sixties. My experience has been that, if you by a new Mikuni (set up for a four stroke engine) from Sudco and leave it jetted as it is out of the box, it will be pretty close no matter what bike you put it on, as long as it's about the right venturi size, and you avoid the temptation to go too large. Another thought would be a Keihin CV carb. James Mosher at performanceindian.com sells a Keihin CV kit for Indians, he might be someone to talk to. Good luck.


Kevin


.

[T. Cotten]

He doesn't want to reinvent the wheel. He wants the specifications from someone else who already reinvented it.

Trust me, he really, truly, honestly wants the information on adapting a Mikuni, not adjusting an XYZ. A separate thread could be started giving all the reasons and opinions why someone should stick with XYZ, but here the question is, what does my friend need to know to switch to Mikuni.

Well BoschZEV..

Everyone gets to play with their toys any way they wish.
And spend their money over and over as well.

But obviously some folks should ask themselves why they want a vintage vehicle in the first place.

....Cotten

[BoschZEV]

My experience has been that, if you by a new Mikuni (set up for a four stroke engine) from Sudco and leave it jetted as it is out of the box, it will be pretty close no matter what bike you put it on, as long as it's about the right venturi size, and you avoid the temptation to go too large. Another thought would be a Keihin CV carb. James Mosher at performanceindian.com sells a Keihin CV kit for Indians, he might be someone to talk to.

Thanks very much for your reply. My one experience with Sudco (for a British single) gave me a carburetor with the jetting quite far off. The slide cutaway was fine, but main jet, needle jet, and pilot jet all required changes. Be that as it may, the issue is what venturi size to buy, and here I'm hoping someone with experience with this conversion will find this thread and offer their experience.

I checked the Indian site and they do for Indian what my friend wants to do for his Harley. Of course, the manifold and linkages are "details" that would be different. Personally, I'm not a fan of CV carburetors, but that's a different issue.

Again, thanks very much for your post.

[exeric]

I have to agree with Tom. The whole allure of vintage vehicles is interacting with the technology of the day, and immersing yourself in the nuances of riding the bike as it was originally designed, and intended. There's a lifetime of dedication required to understanding the world of 1930's and earlier motorcycle technology; let alone hybridizing. Of course it's his bike to do with as he pleases.

[BoschZEV]

But obviously some folks should ask themselves why they want a vintage vehicle in the first place.

The whole allure of vintage vehicles is interacting with the technology of the day, and immersing yourself in the nuances of riding the bike as it was originally designed, and intended.

I worded my original question to try to keep the answers focused on the Mikuni question, but I knew it was going to be futile...

All I'll say is that if "the whole allure" were only interacting with the technology of the day, no one would be be in business selling electronic voltage regulators, electric starter conversions for Gold Stars, LED taillights, CV carburetors for Indians, substitutes for clincher tires, electronic ignition systems, etc. etc. If an entire electric starter system is OK for a Vincent Black Shadow (and some people say it isn't; others say it is), than surely my friend's only choice shouldn't be to either keep it stock or buy a modern motorcycle instead.

[exeric]

I'll always remember looking at a '37 Chief with the late Toney Watson. The Chief had a digital speedometer where the Corbin should have been. . . Toney's comment. . . Nerd cycle !

[T. Cotten]

Golly BoschZEV,...

Folks who pioneered and made these machines legendary weren't 'Rocket Surgeons', so your friend shouldn't need to be either.
But if he thinks he won't have endless variables to deal with (and spend for..) by bolting on a piece of a flying saucer, by all means let him go for it.

Especially if he has a lathe, welding skills, and all the rest that makes it *fun* for many of us.
(NOT ME! I do it for a living dammit.)

But please, please encourage him to keep his DLX20 high and dry!

...Cotten
PS: Maybe you should ask on the Yucky Urinal: http://www.jockeyjournal.com/forum/forumdisplay.php?f=2
But don't mention my name: They barred me for punctuation.

[Shaky Jake]

Whether it is better to augment or not to augment; on this men will never agree...

Let's just hope that he didn't repaint it!



Kevin


.

[Frankenstein]

Having had good results with Mikunis on a variety of flathead and OHV Harleys, I would suggest that the Mikuni marketed for 45's would be a good starting point, re: jets, choke size, etc. I suspect it would give reasonable results out of the box.
Just one man's opinion, "your results may vary"
DL

[BoschZEV]

I would suggest that the Mikuni marketed for 45's would be a good starting point, re: jets, choke size, etc.

Do you know who sells Mikunis for this purpose?

[T. Cotten]

Do you know who sells Mikunis for this purpose?

BoschZEV!

Try your local dirtbike boneyard for a bucket of them.
But beware that swapping various jets and needle settings for tuning is a "given", and new assemblies should come with an arsenal of sizes. Beware also that any rubber boot that you hang it on with will be subject to ever-changing modern fuels.

Yet you will be certain to save some investment in the long run, since anything new out of a box will depreciate as soon as you open the box;
The real thing would appreciate, even just sitting on the shelf.

.....Cotten

[BoschZEV]

But beware that swapping various jets and needle settings for tuning is a "given", and new assemblies should come with an arsenal of sizes.

Old carb or new, getting the jetting correct is part of the process. It's just faster if someone has gone through it before on the same motorcycle, determined the size carb that works best for a particular application, and the jets that work for them. That saves a lot of time. Once a Mikunki is jetted properly it will start, accelerate, idle and do everything well without headache for at least 10,000 miles. Even if the ~$100 for a Mikuni VM depreciated to $0 in that time my friend will have lost all of, um, $100 for having had a trouble-free 10,000 miles. That's why my friend wants one on his bike.