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-   -   Mikuni on an R80 help (http://www.advrider.com/forums/showthread.php?t=824125)

hardwaregrrl 09-06-2012 03:56 PM

Mikuni on an R80 help
 
Hey all. Wondering if any one has base line jet settings for a 32 TM mikuni on an R80 St. Also if you have cable info that would be great too!! Tia

hardwaregrrl 09-06-2012 04:41 PM

They are flat sides. Not going above 6,000 ft

hardwaregrrl 09-06-2012 07:23 PM

Anybody?

ontic 09-06-2012 07:37 PM

Sorry mate,
If it was a VM34, I would have sent you a PM.

What's the story? Do you have these carbs already?

Kai Ju 09-06-2012 09:14 PM

+ on VM's
 
If they were VM's we could get you in the ballpark. No idea on the TM's
What did they come off of ?
Were they meant for an airhead ?
What jetting do they have right now ?

Come to think of it, I had a TM 38 on my Rotax powered Ninja 250 and it uses essentially the same brass that the VM series does.

So here goes:
These are the specs for VM38s on a '77 R100/7


Description Spec
Main Jet 210
Pilot Jet 25
Needle Jet 166 P-8
Jet Needle 6DH3
Slide Cut Away 2 This will likely be different since the TM is a flatslide
Main Air Jet 0.5
Needle Valve Ass'y 3.3

The other option is to call SUDCO and see if they have specs for what you got.
I made my own cables from the stock cables, take your time, measure three times before you cut anything.

hardwaregrrl 09-07-2012 04:54 AM

Thanks! This at least gets me started.....the carbs are brand new. I'm sanding a floor for Nathan Mende of Boxerworks-service and he ordered these for me from parts unlimited in a bit of trade. I was assuming I'd have to make my own cables by grinding the barrel down on the existing cable. I know they're jetted very rich. out of the box..250 main 45 pilot. Needle jet 389 Q-2 jet needle 5FP17. Thanks for the help, I'm racing it again next weekend and am dumb enough to want these carbs on the bike for the rally.

Quote:

Originally Posted by Kai Ju (Post 19538632)
If they were VM's we could get you in the ballpark. No idea on the TM's
What did they come off of ?
Were they meant for an airhead ?
What jetting do they have right now ?

Come to think of it, I had a TM 38 on my Rotax powered Ninja 250 and it uses essentially the same brass that the VM series does.

So here goes:
These are the specs for VM38s on a '77 R100/7


Description Spec
Main Jet 210
Pilot Jet 25
Needle Jet 166 P-8
Jet Needle 6DH3
Slide Cut Away 2 This will likely be different since the TM is a flatslide
Main Air Jet 0.5
Needle Valve Ass'y 3.3

The other option is to call SUDCO and see if they have specs for what you got.
I made my own cables from the stock cables, take your time, measure three times before you cut anything.


ontic 09-07-2012 05:13 AM

Next weekend! Sounds like you've got a busy week:D

I got a couple of these cable kits from Venhill, one for my throttle and one for my choke (because I have changed both the throttle and the choke and about to do the carbs)
http://www.venhill.co.uk/Cables_-_Co...SPILITTER.html

I don't have my mikunis yet, but these kits look like they'll do the job very well. 48mm stroke in the splitter- a bit light and plasticy compared to the bmw splitters, but I suppose it will work just fine.
Aside from all your jetting stuff, you may need to look into the stroke needs of your carbs and what your bmw splitter and throttle can actually provide. Airhead Wrangler helped me out pointing this out with a post of his somewhere a while back.
No point upgrading to mikunis if you can't open right em up:D

Kai Ju 09-07-2012 07:15 AM

Stick with what you got.......
 
..........for right now at least.
A week is not a lot of time to make cables and get carbs dialed in.
Also, depending on what throttle you are planning on using, you may have to modify the gear mechanism to get it to open the slide carbs all the way. The stock setup on mine only gave me about 3/4 throttle. If need be I'll take a pic or two on how I modified mine to give you some idea.
Also, the exposed wire length will be too short to fit the slide so grinding the barrel won't be enough, you'll have to shorten the outer cable to effectively lengthen the inner cable.
Sorry, got to leave for work but pm me if you got questions about cables and such.

supershaft 09-07-2012 11:28 AM

They are brand new? Send then back and get bigger ones!

Beater 09-07-2012 11:51 AM

Quote:

Originally Posted by supershaft (Post 19542497)
They are brand new? Send then back and get bigger ones!

On an R80? The little research I've done here seem to me that the 32 or 34 were the sweet spot for an R80 ... and the 32 provided more low end grunt ... which is what she is going for ...

Am I wrong?

Sniper X 09-07-2012 12:04 PM

Quote:

Originally Posted by Beater (Post 19542650)
On an R80? The little research I've done here seem to me that the 32 or 34 were the sweet spot for an R80 ... and the 32 provided more low end grunt ... which is what she is going for ...

Am I wrong?

Definitely if she won't be venturing above 6000ft and needs more air. I had 40s on my R100RS and up here at 7500ft that was great but I would have done 38s if I had still lived in Monterey at sea level for sure.

Sniper X 09-07-2012 12:04 PM

BTW I want a set for my R80RT so when you do get a good idea of a baseline, let me know and I can calculate with i need to do up here at my altitude.

hardwaregrrl 09-07-2012 04:34 PM

So I know it's a bad idea to be slapping these things on and racing a rally.....but I want to play with my new toy!!:D Hardest part was figuring out the cables. No one has cables for the R80 2-1.....weird. Anyway, I wandered into the back of Cycle Word in Athens GA and found some 4 wheeler cables that are going to work. Had to put a barrel on the end of the carb to get the appropriate free play, but the slides open all the way!! Yippie!!! Going to buy a bunch of jets tomorrow and try to get it dialed in....I know it's a fucking stupid idea.....but if I get it running right and it pulls, by golly whats the problem with racing it !? I'll post up some pics of the install and let you know where I land with jetting... I went with 32s because I don't want bigger I want a bit quicker acceleration, that's it.

@ontic: nice kit, Hans! I just got lucky.....hoping to post up what they are off of so anyone else doing this doesnt have to dig.

@Kai Ju: I just can't stand having a new set of mikunis sitting there.....call me crazy.:loco

And Dean and Nathan did all the brainiac work.

supershaft 09-07-2012 06:11 PM

Quote:

Originally Posted by Beater (Post 19542650)
On an R80? The little research I've done here seem to me that the 32 or 34 were the sweet spot for an R80 ... and the 32 provided more low end grunt ... which is what she is going for ...

Am I wrong?


More low end grunt than 32mm Bings? That could be done with 38mm Mikuni's. I would run 36's for a lot more low end and a lot more high end at the same time but that's just me. Stepping away from Bings you can have it all at once. It's easy to do when you start from such a low performer. :D

hardwaregrrl 09-07-2012 08:48 PM

Welp.....the bike runs very nicely. I just got them on, hooked up and cables loosely adjusted. Didn't feel like taking a ride in the dark with these new guys. Here's a few pics of the cable mod.....had to turn the carbs in a bit more as the cable top was interfering with the HPN tank.

http://i814.photobucket.com/albums/z...3C62033C27.jpg

http://i814.photobucket.com/albums/z...402EF5BC61.jpg

Here's the original cable assembly I stole the cables from.

http://i814.photobucket.com/albums/z...41079766D1.jpg

And the other end.

http://i814.photobucket.com/albums/z...40FCC40281.jpg

And a quick video....please turn you volume down as I don't want you to get pissed at me for being loud.:D

<a href="http://s814.photobucket.com/albums/zz66/hardwaregrrl/?action=view&amp;current=4D868670-F1F1-4EB9-937E-75E201626DC3-4882-0000073C8C4C5D1A.mp4" target="_blank"><img src="http://i814.photobucket.com/albums/zz66/hardwaregrrl/th_4D868670-F1F1-4EB9-937E-75E201626DC3-4882-0000073C8C4C5D1A.jpg" border="0" alt="Uploaded from the Photobucket iPhone App" style="width: 160px;"></a>


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