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Old 10-14-2013, 03:14 PM   #241
hardwaregrrl
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Just an update....I'm now running 160 mains, needle in the middle pos, 22.5 pilots 1 1/2 turns out and needle jet is a #389 series P2. The carbs are TM 32mm. Bike runs well and I may be getting close to getting it on a dyno.
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Old 10-23-2013, 01:16 PM   #242
Twinboy
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Well I finally decided to install the Mikuni 38mm carbs I have had for a while on my 1983 R100.It has a fresh top end and I live at 2500 ft.The bike has a well oiled K&N airbox filter and Bub Sport Exhausts so it breathes well.
Slide 2.5
Pilot jet 25
Main jet 250
Needle 6DH3 clip in second notch
I used the choke cable kit from Rocky Point so the handlebar choke lever works same as with Bings. The throttle response is significantly better and the bike pulls quicker and harder in every gear! it starts easily on choke with a crack of the throttle and a couple of seconds of holding the throttle slightly open. It pulls cleanly with no stutters or surging.
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Old 10-23-2013, 03:11 PM   #243
supershaft
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Quote:
Originally Posted by Twinboy View Post
Well I finally decided to install the Mikuni 38mm carbs I have had for a while on my 1983 R100.It has a fresh top end and I live at 2500 ft.The bike has a well oiled K&N airbox filter and Bub Sport Exhausts so it breathes well.
Slide 2.5
Pilot jet 25
Main jet 250
Needle 6DH3 clip in second notch
I used the choke cable kit from Rocky Point so the handlebar choke lever works same as with Bings. The throttle response is significantly better and the bike pulls quicker and harder in every gear! it starts easily on choke with a crack of the throttle and a couple of seconds of holding the throttle slightly open. It pulls cleanly with no stutters or surging.
It sounds like all you have to do yet is put smaller and smaller mains in it until it pings or cuts out/doesn't run above half throttle in top gear and then put a 'size' or two (250, 245, 240, for instance) bigger back in for best power. For instance, you might find that it runs fine until you get to 200's and then put 210's back in it just to be safe versus 205's. IF that's the case and it very well could be, I would guestimate through experience that you just gained 7 hp with no ill effects other than better mileage and a cleaner running engine. With a stock engine, that is an over 10% power increase for free and then some!

Well, that and drop those needles a notch. Jetting 101: If you make a change leaner and you can't tell any difference, you are too rich. Go leaner yet.

supershaft screwed with this post 10-23-2013 at 03:37 PM
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Old 10-23-2013, 06:27 PM   #244
Twinboy
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Well we started out with 230 mains but it wouldn't pull well until the main jets were increased to 250s. Maybe the better breathing necessitates larger main jets.It really runs very cleanly and strong with the 250s.
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Old 10-25-2013, 11:37 AM   #245
685
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Location: Tucson (east side) AZ
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Here's mine. (Forgive me, this is my first airhead.) It's a Mongrel. Started life as a 71 R75/5, got an engine transplant (76 R90/6) and a new frame 78 R80/7/S (?) My head hurts just thinking about all the money a previous owner threw at this thing.

76 R90/6(?) no fancy engine displacement numbers on the side of the engine case, but that's what the engine number implies. New to all this stuff so I could be mistaken. Previous owner said the engine is bored out to the big bore 1050--whatever pistons.

Mikuni VM38's Tucson altitude is about 4400 ft. A ride to the mountains can reach 9000, tho.

Needle, 2nd slot from the top
Mixture screw was 1/2 turn out, now 1 1/4
Main jets ?
Pilot jets? ( can't read those tiny numbers.)

Just got the bike last weekend. Stinky old gas, leaky carbs, leaky fuel lines. It wouldn't start at all when I got it, some fresh gas with techron helped, but it took taking them off and a good cleaning to get the bike to idle. Left side main was completely blocked--I pushed the crap out with a bit of safety wire and flushed everything with Brakleen.

I'm probably going to soda blast the carbs exteriors and maybe the insides of the float chambers. It was pretty scummy, stored with water in the bowls & stinky gas. Soda blasting is pretty mild and puts some pretty back in the carbs.


So for now, they're clean, not well adjusted. Starts on choke and idles after getting warmed up a little. I haven't had the bike out--first gear is kinda gone (won't stay in gear) and starting out in second is kind of a drag. But I may take it out for a little italian tune up this weekend.

My other bike is an 08 KLR, by definition, I'm a cheap bastard.

This is a great thread. I think I'll go take an Aleve.
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Old 10-25-2013, 12:05 PM   #246
supershaft
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Quote:
Originally Posted by Twinboy View Post
Well we started out with 230 mains but it wouldn't pull well until the main jets were increased to 250s. Maybe the better breathing necessitates larger main jets.It really runs very cleanly and strong with the 250s.
That very well could actually be the case. I am just going on because I have seen the results of people's misguided jetting many times. I guess they are telling themselves something like that as they jet something way too rich. Better breathing? K+N filters (in the stock airbox!) and louder mufflers amount to very little difference if any and what difference it usually does make is right off idle, not up on the mains. Don't get me wrong, you could be spot on but no one really knows what is going on until they start from too lean because what works best is usually just barely richer than that. The further you get off idle the more that becomes true. Again, I am just trying to help but typically when I find setups too lean they are too lean just off idle and too rich on the mains but exceptions do make that rule!
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Old 10-25-2013, 12:17 PM   #247
photorider
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Anybody have numbers for the 26mm carbs used on the R60 and R50?
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Old 11-07-2013, 09:14 AM   #248
Uncle Pollo OP
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hey shaft!

so bike running really well with the homemade velocity stacks and filters.

But at full open kinda hesitates, back off a bit, and surge ... too lean on the main?

Or just go leaner till it does not want to go?

I got plenty smaller mains.

Off idle and midrange pulls like a whip!
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Old 11-07-2013, 09:18 AM   #249
Airhead Wrangler
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Originally Posted by Uncle Pollo View Post
But at full open kinda hesitates, back off a bit, and surge ... too lean on the main?
Sure sounds like it.
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Old 11-07-2013, 09:20 AM   #250
Uncle Pollo OP
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Originally Posted by Airhead Wrangler View Post
Sure sounds like it.
Damn it.

Off to buy 150 and 155 I guess.

If I raise the needles it pops when I close the throttle.

They are in the middle notch with no popping at all.

It is really fun messing with it.
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Old 11-07-2013, 09:22 AM   #251
Airhead Wrangler
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Originally Posted by Uncle Pollo View Post
Damn it.
Either that or your new filter setup doesn't pass enough air at "full suck."
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Old 11-07-2013, 09:27 AM   #252
Uncle Pollo OP
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Originally Posted by Airhead Wrangler View Post
Either that or your new filter setup doesn't pass enough air at "full suck."
At freeway speed it feels normal and pulls to 100 without much drama.

I noticed it at pulling full open and midrange.
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Old 11-07-2013, 01:13 PM   #253
supershaft
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It all depends. Full open? At what rpm and load?

Are you too lean on the mains? Only one way to find out. Put smaller mains in it. SO many people never figure out that jetting takes having jets!

140's in it now. Try 120's. It only takes a minute and if they are too lean you probably can tell within a block or two from your house before you even get on the highway. If it still runs worse with 130's, try 160's. If it runs way better make sure it doesn't also run way better with 150's in it. And so forth.

supershaft screwed with this post 11-07-2013 at 01:19 PM
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Old 11-09-2013, 09:55 AM   #254
Uncle Pollo OP
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Quote:
Originally Posted by supershaft View Post
It all depends. Full open? At what rpm and load?

Are you too lean on the mains? Only one way to find out. Put smaller mains in it. SO many people never figure out that jetting takes having jets!

140's in it now. Try 120's. It only takes a minute and if they are too lean you probably can tell within a block or two from your house before you even get on the highway. If it still runs worse with 130's, try 160's. If it runs way better make sure it doesn't also run way better with 150's in it. And so forth.
just try try try eh?

will do and report back.
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Old 11-09-2013, 12:47 PM   #255
supershaft
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Originally Posted by Uncle Pollo View Post
just try try try eh?

will do and report back.
THAT is jetting!

Mains are the easy part! Off idle and midrange is all about different combos of jets. A leaner slide angle and a richer needle jet might work better than a richer slide angle and a leaner needle jet. Or not. Throw in different jet needles and jet needle positions and the options are considerable. The best news about all that is that it usually just takes a ride around the block to tell what is going on for the most part.
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