Seeking Mikuni TM Smoothbore Expertise

[808BMW]

If you mean modded motors you need to say that, but I disagree with your theory anyway, it depends more on how you run the engine that what mods are done to it.

I assumed since this is in performance technical, and specifically in wheelman's thread about his performance setup, it's a given. But yes, all that applies to big bore bikes.

Like I said, I don't know how oil injected carbs actually perform the injection. I just thought that the oil would puddle up (the same way poor intake manifold designs can lead to puddling of fuel from a fuel injector) and not be effective. If it doesn't then that is cool too, I am completely wrong. I've never worked on an aero, so I didn't know that's how they do it.

As far as blowing your motor due to premixing 2 oz. of oil into 128oz. of gas, I have my doubts. But as far as this thread goes, best of luck Wheelman! Stay away from the smoke when you solder

[Wheelman-111]

Greetings:

Quoth Veedubh:

But as far as this thread goes, best of luck Wheelman! Stay away from the smoke when you solder

Aw, man! That's the only thing I like about soldering! Everybody's gotta be Safety-Boy.

Yeah I wondered how a snot-trickle of GN-2 down the manifold got to do any good to the rings too. Evidently it's scooped up in the gasoline-saturated Intake Hurricane and atomizes/dissolves in sooner or later. Burnt_Toast got me to worrying about the pump output location, and Honda's stock Elite design - squirting into the carb venturi - made that worry worse. But the Aero and the SB50 (I think) have their oil barbs on the manifold, so I figure that's probably OK too.

I'll take you up on your kind offers for a 1/8" barb, and offer anything I have of equal or greater value in return. Our Deepinnaharta Home Depot is hopeless...
High-school Special Curriculum Reject: "Yew want a WHUT?"
All carb parts manufacturers keep their sources for the reasonably-sized threaded barbs a National Secret.

[Wheelman-111]

Greetings:

For the TM-24 carb - which appears to be identical to the Stage6 carb some are running - I started off with the 130 that came in the carb. It ran cooler than the stock carb for sure, but still warmed up off-throttle, sometimes above 400 on coast-down. I went to the 135 and finally 140, seeing temps reined in to max at 350 on coast-down. I still haven't heard it 4-stroke. I haven't checked the plug lately, but the last time I looked (with the 130) it was still Harlequin. Black on one side, White on the other. Excessive oil and a generally too-lean mixture is what I now suspect. More as it develops. The scooter's running great!

[bakaracer]

Greetings:

For the TM-24 carb - which appears to be identical to the Stage6 carb some are running - I started off with the 130 that came in the carb. It ran cooler than the stock carb for sure, but still warmed up off-throttle, sometimes above 400 on coast-down. I went to the 135 and finally 140, seeing temps reined in to max at 350 on coast-down. I still haven't heard it 4-stroke. I haven't checked the plug lately, but the last time I looked (with the 130) it was still Harlequin. Black on one side, White on the other. Excessive oil and a generally too-lean mixture is what I now suspect. More as it develops. The scooter's running great!

The pilot is to small yet if it heats up on close throttle.Another way to know your pilot is lean is let the bike idle and grab a quick handfull of throttle and let go.If it boggs, the pilot is lean.

[Wheelman-111]

Greetings:

God point, Baka. But it doesn't bog with the quick handful test.

Another point to consider is that when I adjust the idle mixture screw it gains RPM as I turn the screw out. It slows markedly when I turn it in to less than 2 turns out. There's no "lean limit" with the 15 pilot, all the way out it keeps revving higher, so it seems to like the added air.

I plan to try a 12.5 when it arrives, but will pay close attention to off-throttle warming.

[bakaracer]

Did you buy that carb used or new?

[Wheelman-111]

Greetings:

The carb was brand new, with 130 Main and #15 Pilot.

[elitedio]

It is easy to make your own cable end wheelman. I used a brass bicycle spoke nipple and cut it down to fit. I use a lathe but I think that a dremel might work as well.

If your cable is not stainless steel it is easy to solder with standard solder and a decent sized gun or iron.

Your carb looks to be a beauty.

[Wheelman-111]

Greetings:

Thanks EliteD. I really am liking this Mikuni, but still fine-tuning the midrange. At Main #140 right now and fixin' to try the 145 this evening. As I rode to work this morning there was a distinct flat spot in the 1/4-1/3 throttle range (where I seem to do a lot of my City riding) due I believe to a bit of leanness on the needle position. I was able to get the stock-ish cable to act just long enough by drilling down the Mik carb cap about 5mm. I can apply throttle by turning the handlebars all the way right... because the casing on the cable Taz sold me is just an inch short.

Soldering a cable from a brass bicycle spoke nipple? That would require two things I have not:
A. A spare brass spoke nipple. (I did pick up some cable-building bits from Beatrice Cycle...)
2. Actual "skills" at soldering. Or anything else. My soldering gun is from the Nixon administration and a bit weak. I need a primer on soldering from someone who knows the craft. I can't get the melted goo to stick to anything but my dining room table.

[elitedio]

soldering is not that hard. go to a bike shop and get some nipples. Or send me a PM and I can send you some. What you need besides an iron or gun is good solder. If you have an iron file the tip till it is shiney. If you have a gun loosen the bolts that hold the tip in and tighten them. Don't use the non-lead solder. I use 40/60 rosin core. You will see the solder joint flow, it isn't done till it does. Don't try and solder stainless steel, aluminum or zinc.

If you get into a job that is too big for your iron you will not get enough heat to make the solder flow. Time to get out the torch.

good luck

[Wheelman-111]

Greetings:

Back to the Mikuni, I jetted up to the 145 tonight and it's still sort of OK but the midrange issue is beginning to feel like a rich situation. It did the flat-spot thing a little with the 140 but a bit more with the 145. Temps definitely appear to be on the way down. I may try just lowering the needle before I go back to the 140.

Thanks for the soldering tips. I'm pretty sure the cables are stainless, aren't they? Maybe it's not ONLY my lack of Skill.

[Wheelman-111]

Greetings:

UPDATE:
Good evening Stage6 and Mikuni TM24 fans. 78cc Nikasil seems to like the idle jet at 12.5, one and a half turns out. I can now adjust to a midpoint, which was not the case with the 15. I couldn't reach the lean max with that one despite going 3 or more turns out.

Having swapped to 145 with midrange issues, I opted first to richen the needle one click from middle of 5. Lean surging once again went away. Power is good throughout now, temps 300 loaded, stay below 350 off-throttle despite the smaller pilot.

[mousewheels]

I'm pretty sure the cables are stainless, aren't they? Maybe it's not ONLY my lack of Skill.

A flux for stainless helps a lot. Part will require cleaning to remove the flux afterwards, its corrosive.

Here's a pic of a cable I soldered up. This is a solder sample only, no strength in the bitty lap joint. Had there been a cable end around I'd have used it.

[Wheelman-111]

Greetings:

Nice work, and nice pics, Mouse!

So do you start by painting the clean metal with the flux er whut?

I cleaned the metal with acetone, Fluxed it with some unidentified clear liquid meant for silver, heated it with my Weller gun, touched the solder to the joint, then hit the dining room table with the fire extinguisher. Not a drop of the solder stayed anywhere near the cable the first seven times. When I finaly got what I thought was a bond, I found I could pull the cable end off with my fingernails.

Maybe somebody could YouTube a Cable-End Soldering for Dummies sometime.

[mousewheels]

I cleaned the metal with acetone, Fluxed it with some unidentified clear liquid meant for silver, heated it with my Weller gun, touched the solder to the joint, then hit the dining room table with the fire extinguisher. Not a drop of the solder stayed anywhere near the cable the first seven times.

Gee, that sound like good process and flux.

--- Mousewheels methods:
Set up the parts so they will not move. Start poking the joint with solder as soon as the flux sizzles(if using liquid flux. Otherwise just poke until it flows). As soon as solder flows it is fed constantly and as rapidly as the joint will take until the desired fillet is present. Then the iron is immediately removed. Hot iron, quick work reduces heat damage to surrounding parts. Opinion: Quick feed keeps joint temperature from climbing any higher, avoiding an overheated joint, burnt out flux.

--- Pre-tin difficult to solder parts
Put a light coat of flux on the cable alone, then 'tin it' with a thin coat of solder. Insert it in to the cable end, and solder as usual. When the joint is up to temperature, solder on the cable and the fresh solder will very readily flow together - IMHO faster and easier than creating the wetting at joining time.

Readers - note this is a solder demonstration to show how a tinned stainless cable will solder., The rule is - First make a good secure mechanical joint, *then solder*. A cable spliced this way never has a place in a critical part like a brake. I'd not use it for an oil pump or throttle cable either. Keeping a pen from walking off at work - yeah

Pic below shows pre-tinning, and the final joint. Black spots on the cable are flux and will go away after cleaning.