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DUAL Mikuni TM38 flat slides Part 2

P901 Single carb intake, FLAASH Cams, Super Charger, NOS.......
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DUAL Mikuni TM38 flat slides Part 2

PostAuthor: ivogiev » Thu Apr 13, 2017 1:30 am

Continued from Part 1 viewtopic.php?f=34&t=55832

Dave, sorry if it sounded as if I am trying to find faults in your setup - that is not the case.
I have bought TM38-85s, I have raised the needles to top position and have printed your 3D files for adapters.
I am going 100% after your setup , just noticed something that may have affected you in a way. If that is not true, I am happy to hear it.
But it was just something I wouldn't leave without mentioning , cause it could have mean you are not 100% opening the slides on WOT.
Thank you for all the advice and shared know-how, I am not in any way decrying your efforts and result.

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Re: DUAL Mikuni TM38 flat slides

PostAuthor: ivogiev » Sat Apr 22, 2017 12:07 pm

Dave,
I was wondering how many turns out of soft seat do you run your idle screw on you original set up?
I have read the thread few times, but nowhere is written the exact amount and it would be useful for followers like me with the same set up.
Mine at the moment is 2,5 turns out of soft seat.
Was 2 turns and backed it out 0,5 turn - nothing changed on idle and decided to leave it as is,because before that it was massive rich on idle.
Got my bike home - runs a ton stronger than with the stock set up, but is a bit loud with my new exhaust.

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Re: DUAL Mikuni TM38 flat slides

PostAuthor: Brodie » Sat Apr 22, 2017 4:42 pm

I have installed mine and I am very impressed. Beats my old worn out mikunis. Have not taken her for a ride yet but it idles a lot nicer and is easy to tune the idle.

I need a new exhaust and am still waiting on my throttle cable but I will post again once I have taken her for a ride.
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Re: DUAL Mikuni TM38 flat slides

PostAuthor: DGA » Sat Apr 22, 2017 10:28 pm

Remember, the idle mixture screws are AIR screws, opening them or going anticlockwise LEANS the idle mixture. I am at 1.5 turns open now, but I have different cams now as well. I think it was too lean with the stock settings, you might try 2 turns open, I seem to recall they were set at 2.5 turns open from stock. If you get a high idle cold, and inconsistent idle speed it means they are set too lean. Go out a quarter turn at a time and try. As you know, you need a really long small flat bladed screwdriver to adjust them.
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Re: DUAL Mikuni TM38 flat slides

PostAuthor: cookeal » Fri Apr 28, 2017 2:50 pm

Having been in several circles regarding carb choice for my XV750 83, finally have found this thread and it feels like the right way to go. Was not really comfortable with the single carb approach for lots of reasons, and having spoken to a few of the makers felt like their claims were a bit too good to be true, and I would end up with a pokey-out carb, and be quite a bit poorer!

So am about to order the carbs (TM-38-85) and just have a couple of questions:

1. Would really appreciate the 3D print file for the connectors - will PM my email address
2. Petcocks - remain standard with the vacuum lines to the inlets?
3. Air Filter - Airbox has already gone so would appreciate any recommendations here?
4. The 2 into 1 cable does not appear to be available any more (on ebay) - any other known sources?

Much appreciated

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Re: DUAL Mikuni TM38 flat slides

PostAuthor: DGA » Fri Apr 28, 2017 4:00 pm

1. Answered in PM
2. Standard petcocks work fine.
3. Ditch the entire stock air filter assembly, even the rubber bellmouth in the frame inlet. Leave the two in the frame just before the rubber 90 degree carb bends. I machined an adapter from the frame to mount a 4" clamp size round air filter, but any decent round filter will work, just as long as you start with the frame inlet and all the crap before it is gone.
4. The cable from Niche cycle in this page http://www.ebay.com/itm/Yamaha-XS650-34 ... gg&vxp=mtr
looks like the right one, might contact them and ask. Niche cycle have good prices on the TM38 anyway, they might include it as a deal if you talk to them.
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Re: DUAL Mikuni TM38 flat slides

PostAuthor: Brodie » Wed May 17, 2017 5:18 pm

I have not had much time to work on these but from what I have done I can add some info.

The replacement stock intake boots I bought seem to be just a slight bit to large but do compress down once you tighten the clamps. The stock cars fit snug before they were clamped.

With the needles set to the highest setting I seem to blow black smoke when I rev the engine without load or an intake setup.

The throttle cable from Mikuni Oz does not fit without modification. I had to shorten the main cable and fit the stock end adjuster.
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Re: DUAL Mikuni TM38 flat slides Part 2

PostAuthor: ivogiev » Tue May 30, 2017 5:19 am

Maybe it would be good to post my input on the same topic.
I followed DGA's setup as it was originally, but my bike doesn't like those settings.
I have risen the needles to their max settings and it was way too rich. Couldn't influence it with the AIR idle screw on the inside of the carbs.
The float height was checked just in case and appeared to be OK and equal on both carbs( that was the only thing I didn't check when installed them on the bike).
I have restored the needle settings to their default middle position and the bike stopped throwing flames and banging on deceleration.
I just had the test ride last night, but other issues are arising that affect the performance.
It starts very difficult and on 1 cylinder most of the times, so my next move will be to change the spark plugs again cause they had a hard time working when the bike was way too rich.
I hope this will bring consistency to my test rides.
My air filter is K&N replacement unit without airbox on it - it is sitting on the frame and breathes as much as it can through the frame.
My exhaust is a custom 2-1 short SS system with calculated diameter and length of the runners. The end "can" is very short and basically I doubt a more free flowing exhaust system is possible.

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Re: DUAL Mikuni TM38 flat slides Part 2

PostAuthor: Brodie » Fri Jun 09, 2017 7:56 pm

Ok I have had a quick chance to give these carbs a bit of a go. From what I have found on my bike (XV1100 '90) The pilot jets are way to rich. I have given the bike a few runs and each time I have had to change the plugs to make it back home after about 200m. That is with 22.5 jets and 2 turns out.
I am at 3 turns out now and it is still very rich when on idle. I was going to order some 17.5 jets but just wanted to see if any one thought I should try the 20 jets before dropping down so far. I have run BP6ES plugs and have just stepped up to BP5ES to try and combat how rich it is running. Just so people know I am a total novice at tuning but I am willing to give it a go. Here is a quick shot of the bike as she sits. Undecided on the shape of the seat so that is why there is not a proper cover.
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Re: DUAL Mikuni TM38 flat slides Part 2

PostAuthor: tymck7 » Tue Jun 13, 2017 7:44 pm

Everyone:

This topic has been extremely interesting and helpful! As the new owner of a completely stock '83 xv750 (and possibly because I came from riding a pretty fast 2005 WR450F supermoto) I've been looking for some decent power adding mods that are reasonable. I'm pretty stoked to try out the TM38-85's.

DGA:

Thank you so much for being the guinea pig on this! I wanted to ask you, what's your elevation over there in Indiana (saw your license plate in your video)? I'm over here in Idaho (1800' give or take) and I ride up into Utah routinely (4500' or more). Wondering if you're close enough to my elevation to where I won't need to drop the needle or switch out the main jet/pilot jet etc... Also, I don't own a 3D printer, but I think your connectors are pretty sweet. What would you charge me to print a couple and ship them my way (I think you deserve something on top of shipping/materials for your trouble putting this all together)? PM me if that's something you'd be willing to do.

- Tyler
stock '83 xv750.. but not for long...

Plans: TR1 tank, R6 front end, XT600 rear shock, dual mikuni TM38's, pod filters, drilled stock pipes, cafe seat, CNC subframe, and anything else cool I read about on here).

Thanks all!

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