ADVrider

Go Back   ADVrider > Bikes > Old's Cool > Airheads
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 03-22-2013, 05:31 PM   #106
oldroadie
Two wheel addict
 
Joined: Feb 2010
Location: North Alabama mountains
Oddometer: 456
I'll be surprised if you don't find that too fat. I have a fairly free breathing R75 and I'm down to 180 and its still a touch rich.
oldroadie is offline   Reply With Quote
Old 03-22-2013, 05:43 PM   #107
blaine.hale
Beastly Adventurer
 
blaine.hale's Avatar
 
Joined: Feb 2009
Location: Atlanta, Ga
Oddometer: 2,925
What are you guys using on the engine side of the carb for the boot? The stock one seems way too big for the mikuni. Mine may be a bit stretched but the bings still fit the stock boot nicely.
__________________
1974 BMW R90 /6
1968 Bultaco Matador MK3
1973 BMW R75 /5 Toaster LWB
1969 Bultaco Bandido MK2
2013 Husqvarna Terra TR650
blaine.hale is offline   Reply With Quote
Old 03-23-2013, 01:48 AM   #108
Kt-88
I like everything.
 
Kt-88's Avatar
 
Joined: Sep 2012
Location: SLC area, Utah
Oddometer: 459
Quote:
Originally Posted by blaine.hale View Post
What are you guys using on the engine side of the carb for the boot? The stock one seems way too big for the mikuni. Mine may be a bit stretched but the bings still fit the stock boot nicely.
Which Bings did you have before? My intake rubbers are fresh but stock and they're peachy.
Kt-88 is offline   Reply With Quote
Old 03-23-2013, 11:16 AM   #109
blaine.hale
Beastly Adventurer
 
blaine.hale's Avatar
 
Joined: Feb 2009
Location: Atlanta, Ga
Oddometer: 2,925
Quote:
Originally Posted by Kt-88 View Post
Which Bings did you have before? My intake rubbers are fresh but stock and they're peachy.
Just running the stock bings for the r90.
I tried it on the unmolested r75 as well, again the rubber is far too big. The engine side of the bings are a fair amount bigger than the mikunis that I have.
__________________
1974 BMW R90 /6
1968 Bultaco Matador MK3
1973 BMW R75 /5 Toaster LWB
1969 Bultaco Bandido MK2
2013 Husqvarna Terra TR650
blaine.hale is offline   Reply With Quote
Old 03-23-2013, 01:55 PM   #110
Kt-88
I like everything.
 
Kt-88's Avatar
 
Joined: Sep 2012
Location: SLC area, Utah
Oddometer: 459
I wonder if mine are just soft enough to make it work? I recall tightening then a good bit.
Kt-88 is offline   Reply With Quote
Old 03-23-2013, 03:59 PM   #111
Beemerboff
Beastly Adventurer
 
Joined: May 2005
Oddometer: 2,221
If you go back to my previous post there is a link to Amal moulded adapters which work well for me, on Miks and Bings.

They are reduced to 28 mm in diameter for about 6mm in the centre, which lets you blend the carb to the stub, and I find that setting the carb back a little also improves things, with the set up on my bikes.
__________________
Adelaide Hills, Australia. 93 R100 GS, 77 R75/7 ,70 BSA B44VS, , 86 R80 G/S PD, 95 BMW Funduro F650 ST
Beemerboff is offline   Reply With Quote
Old 03-23-2013, 06:08 PM   #112
Airhead Wrangler
Adios Mexico
 
Airhead Wrangler's Avatar
 
Joined: Mar 2008
Location: Back in Seattle, FINALLY
Oddometer: 6,341
Quote:
Originally Posted by blaine.hale View Post
Just running the stock bings for the r90.
I tried it on the unmolested r75 as well, again the rubber is far too big. The engine side of the bings are a fair amount bigger than the mikunis that I have.

What size mikunis are we talking about here. I had to use 40mm bing rubbers with 32mm bing rubbers sleeved inside them to fit VM34s onto some big port heads. They fit like a glove though.

__________________
R80ST Gets The HPN Treatment
Seattle to TDF on an airhead

Current rides: HPN #834, '93 R100GSPD "red rocket", '73 R75/5 Toaster mongrel, '80 Ducati Pantah 500SL, '92 DR350, '67 Honda SS50, '80 Honda Chaly.
Airhead Wrangler is offline   Reply With Quote
Old 03-23-2013, 06:17 PM   #113
Kt-88
I like everything.
 
Kt-88's Avatar
 
Joined: Sep 2012
Location: SLC area, Utah
Oddometer: 459
I'll snap pics of mine tonight!
Kt-88 is offline   Reply With Quote
Old 03-24-2013, 01:12 PM   #114
blaine.hale
Beastly Adventurer
 
blaine.hale's Avatar
 
Joined: Feb 2009
Location: Atlanta, Ga
Oddometer: 2,925
Quote:
Originally Posted by Airhead Wrangler View Post
What size mikunis are we talking about here. I had to use 40mm bing rubbers with 32mm bing rubbers sleeved inside them to fit VM34s onto some big port heads. They fit like a glove though.

We're talking 34mm mikunis replacing the completely stock r90 setup.
I might go with what you have there, actually. I'm going to run to the auto parts store and check for some radiator hoses.
__________________
1974 BMW R90 /6
1968 Bultaco Matador MK3
1973 BMW R75 /5 Toaster LWB
1969 Bultaco Bandido MK2
2013 Husqvarna Terra TR650
blaine.hale is offline   Reply With Quote
Old 03-24-2013, 02:36 PM   #115
bgoodsoil
Dare to be Stupid
 
bgoodsoil's Avatar
 
Joined: Jul 2008
Location: Washington, DC, USA
Oddometer: 4,230
__________________
'85 BMW r80G/S--Another G/S on the road--Central America on a Shoestring--Nova Scotia on a Shoestring--Never Leave a Man's Behind

Proud SmugMug User Support ADV: Don't give those cheap bums your discount code
bgoodsoil is offline   Reply With Quote
Old 03-24-2013, 03:07 PM   #116
supershaft
because I can
 
Joined: Sep 2010
Location: San Francisco Bay area
Oddometer: 8,275
Quote:
Originally Posted by oldroadie View Post
I'll be surprised if you don't find that too fat. I have a fairly free breathing R75 and I'm down to 180 and its still a touch rich.
I have a good friend that I use to help dyno jet dozens of airhead/Mikuni setups when we worked at San Jose BMW. Neither one of us can remember for sure what we usually ended up with. I am guessing 160 or 180?

A lot of it depends on whether or not it is a big port or a small port and the airbox setup. In my experience, the air cleaner setup matters way more than the exhaust.

I am just trying to help but I have seen open exhaust call for richer off idle jetting but leaner mains SO many times. It's not counter intuitive IF you realize that they were already way too fat on top with the stock pipes.
supershaft is offline   Reply With Quote
Old 03-24-2013, 05:20 PM   #117
oldroadie
Two wheel addict
 
Joined: Feb 2010
Location: North Alabama mountains
Oddometer: 456
I'm trying 170s next since I have them in hand. Off idle is fine but over 1/2 it seems "soggy" so I'm thinking a leaner main will help. R75/5 with stock airbox and K&N filter, stock headers with crossover pipe and Lowbrow Customs shorty mufflers.
oldroadie is offline   Reply With Quote
Old 03-24-2013, 05:45 PM   #118
supershaft
because I can
 
Joined: Sep 2010
Location: San Francisco Bay area
Oddometer: 8,275
Quote:
Originally Posted by oldroadie View Post
I'm trying 170s next since I have them in hand. Off idle is fine but over 1/2 it seems "soggy" so I'm thinking a leaner main will help. R75/5 with stock airbox and K&N filter, stock headers with crossover pipe and Lowbrow Customs shorty mufflers.
IMO, Bing, Mikuni, and Dellorto have misleading throttle/jet diagrams in their manuals. For starters, it ALL depends on the load. But overall over half throttle is mostly about the mains. The mains are IMO the easiest to jet. Put smaller mains in until it pings or cuts out and then go back up five numbers. ten if your nervous. That's it. I haven't absolutely dialed mine in with my current setup yet.

My last set up (with Dellortos) ran better and better starting with 160 mains. 155's? No difference. 150's? No difference. 145's? It seemed to be revving quicker. 140's? Most definitely running a lot better. 135's? Better yet. 130's? Better yet. 125's? Pulling into the passing lane the bike flat out would not run above about 5000rpm. Like hitting the kill switch. I went back to 135's just to be safe since I have still never pulled top gear. I don't want a 120+ mph speeding ticket. Besides, I already can get one of those pulling 8,000rpm in fourth. That I have done. Then I dyno'ed it and the 135's were a bit rich so I ended up with 130's. That's pretty much how jetting mains go.

With my new setup I am running 165's but going from 8.5:1 to 10.0:1 and really changing the port shapes a lot made a BIG difference. That and now I have really opened up the airbox which would before kill my midrange. I know 155's are too lean. But I have not tried 160's yet since I was still breaking in the engine. I know a real steep uphill freeway on ramp that I can pull 8k in fourth before I get on the highway. I will try a 160 there sometime soon.

You will never know until you try it! SO many people never figure out that in order to jet carbs you need to buy jets. Way more than you will use. That is if you want to figure out what works best. Especially off idle. Mikuni's and Dell's especially work different off idle with different jet combos. You will never know what combo works best until you try the different combos. That's a lot of jets AND slides! For some reason a leaner slide and a richer needle jet might work better than a richer slide and a leaner needle jet. Swap the jet needle and it might all add up differently. You never know until you try it and that takes jets! The only saving grace about just off idle is that you can tell a lot by just going around the block unlike jetting the mains. Good luck!

supershaft screwed with this post 03-24-2013 at 11:09 PM
supershaft is offline   Reply With Quote
Old 03-25-2013, 12:02 PM   #119
blaine.hale
Beastly Adventurer
 
blaine.hale's Avatar
 
Joined: Feb 2009
Location: Atlanta, Ga
Oddometer: 2,925
Perfect fit on the carb side. I'll try the air box side tonight.

__________________
1974 BMW R90 /6
1968 Bultaco Matador MK3
1973 BMW R75 /5 Toaster LWB
1969 Bultaco Bandido MK2
2013 Husqvarna Terra TR650
blaine.hale is offline   Reply With Quote
Old 03-25-2013, 12:38 PM   #120
radicole
Adventurer
 
Joined: Jun 2011
Location: Brooklyn, NY
Oddometer: 18
Hey Blaine,

I also got my Mikuni's from Alpha Moto about a year ago. I used the 210 mains he sent loosely and it was perfect on my R90/6. I used the stock rubber on the engine side and used rubber reducers from my local hardware store to connect to the airbox. Took about an hour to get em installed and it started immediately. I just played with the idle and air screw but it was a huge difference over the Bings. My bike used to crank for like 25 secs before firing up using the Bings. With the Mikuni's it fires up immediately, everytime (knock on wood).
radicole is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 09:26 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014