Mikuni on an R80 help

[ontic]

might be worth having a look at for reference.
http://www.braigasen.com/Mikuni_jett...our_stroke.htm

[sithndman]

Good luck and have a ton of fun!!!

Originally Posted by hardwaregrrl

Oh man I owe you. Going to keep the jets for a bit to make sure it's right. Then I'll add mine in for the next lucky contestant!!!!. Getting my wheels balanced at cycle gear right now then home to check fluids, valves, tools, spares a remount the wheels!!!

[hardwaregrrl]

So, these carbs are pissing me off. I'm returning 27mpg, not riding the bike much differently. I've been told mikuni doesn't list rich to lean on jet needles, and my needle jet is a Q2, theyre are 13 leaner needle jets. How many should I get? I cannot believe that I know people with VMs that are getting over 40mpg. Main jet is 155 now, pilot is 20 1 turn out, can't change the cutaway. What the fuck....yeah I spelled it out. I'm sick of this shit. I hate my Bings but they may be going back on. Any advice beside smart ass shit.....? I'm serious....don't poke the bear.

[RecycledRS]

A couple of thoughts, if your running WFO while racing I doubt you'll see 40+mpg.

Also a #20 pilot sounds a bit small ( 30 or 35 maybe) in my experience. Try going leaner by 2 needle sizes.

[Kai Ju]

Here is Sudco's jetting page where you can find the info you're looking for:
http://www.sudco.com/Carburetor02.html

It does list leaner to richer for the individual components.

How does it run with the needle in the leanest position ?
How do the plugs look ?
Where do you spend most of your time ? Get your mind out of the gutter, I mean in terms of throttle position.
How much time do you actually spend at full throttle ?
How do the plugs look ?

Get a piece of tape, stick it on the throttle housing and mark where zero, half and full throttle are.
Ride the bike and spend time at each throttle setting, evaluating how it runs. Does it feel rich at half throttle ? Full throttle ? etc.
Have you done a plug chop ?
I know, lots of questions but unless you have somebody else's known specs you'll have to find your own.

I am getting 40mpg on my R100 with VM38s and a 210 mainjet in mixed riding. That means I spent most of my time between 1/4 and 3/4 throttle.
Start by dropping your needles, evaluate what happens, look at the Mikuni charts and let us know what happens.

[supershaft]

Poke the bear? I always want to snuggle with the bear. I have the cutest wild cat I sure wish I could snuggle with! A friend of mine has dyno tuned a bunch of airheads with round slides but he can't remember the numbers. I can't either. Sorry. I usually try my best but I am out of the loop on Mikuni's right now.

[Les_Garten]

Originally Posted by hardwaregrrl

So, these carbs are pissing me off. I'm returning 27mpg, not riding the bike much differently. I've been told mikuni doesn't list rich to lean on jet needles, and my needle jet is a Q2, theyre are 13 leaner needle jets. How many should I get? I cannot believe that I know people with VMs that are getting over 40mpg. Main jet is 155 now, pilot is 20 1 turn out, can't change the cutaway. What the fuck....yeah I spelled it out. I'm sick of this shit. I hate my Bings but they may be going back on. Any advice beside smart ass shit.....? I'm serious....don't poke the bear.

I feel your pain...

I am in the process of redoing my bike.

I put Mikuni 40mm Flatslides on mine back in '92.

My carbs have accelerator pumps. I turned them off because they could throw a stream of fuel about 10' literally.

I also went to bings for a while because of gas mileage.

I am however redoing mine with the 40mm Flatslides again.

I won't get into the weeds on all the details till it's done and I post a thread. But the gist of it is that IMO, you need to tune the bike with an Air Fuel Mixture gauge.

If I were you, and I know you're pretty serious about this, I would have an O2 bung welded into one of the headers. Doesn't cost much. Buy an Innovate LC-1 or something like that. I has to be a wideband O2 sensor. Need to really get a good one.

Mark your throttle grip with whiteout or something temporary at 1/4 -- 1/2 -- 3/4 -- Full throttle marks.

Then you can tune that baby perfectly. All other means will be guesses and approximations. You'll have it too lean at some points and too rich at others. IMO, you'll never get it right without doing it this way.

Then you'll be done and you'll KNOW it's right. The bike will be at it's best, and your MPG will be at it's best.

Then you can reference your thread you'll write up and sell the LC-1 at 3/4 what you paid for it and smile!

Some Forums have tool loaner programs were someone donates a tool to the round and the tool travels. This would be a good candidate for a tool loaner program.

p.s. That Sudco tuning manual is worth what they are asking for it.

[hardwaregrrl]

Thanks guys!!! I'd like to stress this is my only bike. I do not race it every day Most of my time is spent....on the highway. Around 4800-5200 rpm, 3/4 throttle. I just(for the hell of it) took the main from 175 to 155 and It had a flat spot and ran rough. I put the 165 main in and it felt better. I agree that the pilot is too small, but that will not effect my fuel mileage. I turned in a half of turn and the bike starts fine on full choke cold. I talked to Sudco (guy wasn't that helpful) and he told me that the jet needle in the TM32 isn't listed from Mikuni rich to lean....and looking at the catalog, he's right. The only thing I can do at this time is needle jet. It came with 389-Q2 which are toward the rich end. O0 being the leanest.....and they climb in increments of 2. Plug looks good, a bit dry fouled. Needle is at the leanest position and the bike runs fine. I spend very little to no time at WFO. I am the only person that I know of that is running 32mm flatsides on an R80.

I'm heading to the swap meet at Barber Vintage tomorrow and I know I'll be able to pick up some jets, and would like to know is where to start as far as what needle jets to look for. Start in the mid P's, or all the way to O's. Here's the chart I was thinking a P2 and O2....

I cannot change the jet needle according to the guy at Sudco as they cannot tell what is lean and what is rich. The needle is obviously my problem as I do not live on my bike at WFO.......but that would be fun.

[Kai Ju]

I cannot change the jet needle according to the guy at Sudco as they cannot tell what is lean and what is rich. The needle is obviously my problem as I do not live on my bike at WFO.......but that would be fun.
__________________

You may not be able to tell rich or lean but the larger the diameter the smaller the annular ring will be between the needle and the needle jet.
Look up your needle jet and get a fatter one. That will make it run leaner.
I'd still suggest what I'm running in my VM38s because I'd think that the smaller flatslides aren't far off in airflow to the larger VMs.
I'm jealous about Barber, I've never been there.......

[robtg]

Originally Posted by hardwaregrrl

Thanks guys!!! I'd like to stress this is my only bike. I do not race it every day Most of my time is spent....on the highway. Around 4800-5200 rpm, 3/4 throttle. I just(for the hell of it) took the main from 175 to 155 and It had a flat spot and ran rough. I put the 165 main in and it felt better. I agree that the pilot is too small, but that will not effect my fuel mileage. I turned in a half of turn and the bike starts fine on full choke cold. I talked to Sudco (guy wasn't that helpful) and he told me that the jet needle in the TM32 isn't listed from Mikuni rich to lean....and looking at the catalog, he's right. The only thing I can do at this time is needle jet. It came with 389-Q2 which are toward the rich end. O0 being the leanest.....and they climb in increments of 2. Plug looks good, a bit dry fouled. Needle is at the leanest position and the bike runs fine. I spend very little to no time at WFO. I am the only person that I know of that is running 32mm flatsides on an R80.

I'm heading to the swap meet at Barber Vintage tomorrow and I know I'll be able to pick up some jets, and would like to know is where to start as far as what needle jets to look for. Start in the mid P's, or all the way to O's. Here's the chart I was thinking a P2 and O2....

I cannot change the jet needle according to the guy at Sudco as they cannot tell what is lean and what is rich. The needle is obviously my problem as I do not live on my bike at WFO.......but that would be fun.

..... " I am the only person that I know of that is running 32mm flatsides on an R80".......There may be a good reason for that. VM36's or maybe even 34's would be better. Nothing wrong with flatslides, but 32's are a bit small.

[hardwaregrrl]

Originally Posted by robtg

..... " I am the only person that I know of that is running 32mm flatsides on an R80".......There may be a good reason for that. VM36's or maybe even 34's would be better. Nothing wrong with flatslides, but 32's are a bit small.

thanks for your help

[supershaft]

I wil try to help. All carbs jet the same. The difference carb to carb is how much and where the jets overlap.

I haven't read all the posts but it sounded like you found too lean on the mains. Just richer than too lean is perfect on the mains. Don't go back too rich. A bigger needle jet (richer) mainly effects just off idle to quarter throttle. A different base diameter jet needle does the same thing. The other biggie is the slide angle and they effect about the same range. BIG mileage changers since you are in these jets during a lot of cruise. Slides are expensive but you can make them leaner with a file. The tricky part is matching them on multi-cylinder bikes.

Idle jets do not turn off out of their effective range. Too rich an idle jet WILL effect mileage.

Part of the trick jetting just off idle is that different combo's of slide angle/needle jets/jet needles/idle jets do different things. To really find out what works best, you have to try a lot of different combo's. It's a lot of time and a lot of jets (times two!).

Like I always advise about Bings, it says right in the Sudco manual somewhere that needle jets are crucial. It really is true with Dell's too. That and the slide angle makes all the difference in the world. Good luck and I hope I am not poking the bear!

[hardwaregrrl]

Originally Posted by supershaft

I wil try to help. All carbs jet the same. The difference carb to carb is how much and where the jets overlap.

I haven't read all the posts but it sounded like you found too lean on the mains. Just richer than too lean is perfect on the mains. Don't go back too rich. A bigger needle jet (richer) mainly effects just off idle to quarter throttle. A different base diameter jet needle does the same thing. The other biggie is the slide angle and they effect about the same range. BIG mileage changers since you are in these jets during a lot of cruise. Slides are expensive but you can make them leaner with a file. The tricky part is matching them on multi-cylinder bikes.

Idle jets do not turn off out of their effective range. Too rich an idle jet WILL effect mileage.

Part of the trick jetting just off idle is that different combo's of slide angle/needle jets/jet needles/idle jets do different things. To really find out what works best, you have to try a lot of different combo's. It's a lot of time and a lot of jets (times two!).

Like I always advise about Bings, it says right in the Sudco manual somewhere that needle jets are crucial. It really is true with Dell's too. That and the slide angle makes all the difference in the world. Good luck and I hope I am not poking the bear!

Thanks Billy! I struck out at Barber as no one had a Mikuni tune up box....weird....lots of Amal stuff though.

I'm planning on mimicking the VM32 needle jet and jet needle. I think P4 or P2 will do it...and not sure which jet needle yet. I'm going to keep the mains around 160/165, don't want to change too much at once. I won't touch the slide, that scares me and I think none other are avaliable for the TM series, again not sure. I may just shelve them and buy another spliter and just swap the Mikunis on before race day. But that developes another problem, throttling out of turns will be a learning process while racing. That might be a stoopid idear!

[Uncle Pollo]

Originally Posted by hardwaregrrl

So, these carbs are pissing me off. I'm returning 27mpg, not riding the bike much differently. I've been told mikuni doesn't list rich to lean on jet needles, and my needle jet is a Q2, theyre are 13 leaner needle jets. How many should I get? I cannot believe that I know people with VMs that are getting over 40mpg. Main jet is 155 now, pilot is 20 1 turn out, can't change the cutaway. What the fuck....yeah I spelled it out. I'm sick of this shit. I hate my Bings but they may be going back on. Any advice beside smart ass shit.....? I'm serious....don't poke the bear.

ihave the one on my signature that its a hair too rich. the next leaner one is in the mail. i am certain that it would work if the air density was higher here. try that one. i am getting the two next richer pilot jetts too ... reading sparkplugs is easy . chocolate color is what you want. my mainn is dialed in as far i can tell. top rmp top gear full open = chocolate. running around town is darker and getting 45 mpg. but i am riding like an asshole too.

[RecycledRS]

Chocolate brown is too rich IMO.