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 Post subject: Wanted, the recomended jetting sizes for Mikuni TM41
PostPosted: Sat Dec 11, 2010 4:09 am 
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Joined: Sun Nov 07, 2010 10:54 pm
Posts: 425
Location: Brisbane
Looking to buy a pair of Mikuni TM Pro Series 41mm
Has any one used these on a 750?
What jet sizes work best?
Where is the cheapest place to buy a pair?

The jets are expensive in Australia, so if I can buy them prejeted it will save me lots of time and money.

Thanks
Graeme


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 Post subject: Re: Wanted, the recomended jetting sizes for Mikuni TM41
PostPosted: Sat Dec 11, 2010 1:04 pm 
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Joined: Mon Oct 04, 2010 7:47 am
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Graeme,

How is the motor setup? Displacement, compression, cams, valve sizes? Are these for the heads you sent pictures of? Are you going to run air cleaners? Which I strongly recommend. What type of fuel are you going to be using?

I have run these on the race bike with good success and Steve had good luck on he's F1 853.

Sudco International here in the states has fair prices. With a little information I can probably get you close on jetting, slides and needles.

Palmer


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 Post subject: Re: Wanted, the recomended jetting sizes for Mikuni TM41
PostPosted: Sat Dec 11, 2010 5:28 pm 
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Joined: Sun Nov 07, 2010 10:54 pm
Posts: 425
Location: Brisbane
Hello Palmer,

748, 88 x 61.5
12.3 :1
2 x front 900ie cams, 25/75 inlet and 66/28 exhaust
duration 280 degrees inlet and 274 exhaust
lift 11.8 inlet and 11.4 exhaust
valves are 41 and 35.

Yes the heads that I sent pics of.
front is 98 cfm @ .45" lift. rear is 100 cfm @ .45" lift, through the 40mm Dellortos.
I've spoken to the fellow who did the flowing and asked if I should look at 38 or 41 TM's and he thought they could handle the 41's. But he is in a workshop and not in real life using them, so suggestions accepted please.

Yes, air cleaners, I can't see the point in spending heaps of $ on an engine and putting sand in it.

Premium 98 unleaded, no ethanol (at this time)

Regards
Graeme


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 Post subject: Re: Wanted, the recomended jetting sizes for Mikuni TM41
PostPosted: Sat Dec 11, 2010 11:36 pm 
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Joined: Fri Oct 15, 2010 12:20 pm
Posts: 1186
Location: Vermont, USA
Have you seen these guys?

http://www.motorcyclecarbs.com/Mikuni_T ... 9C2322.cfm

Bill


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 Post subject: Re: Wanted, the recomended jetting sizes for Mikuni TM41
PostPosted: Sun Dec 12, 2010 1:14 am 
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Joined: Thu Oct 14, 2010 7:30 am
Posts: 138
Graeme, I've found the list I made on my F1 jetting. I'm using NCR #7 cams which have a bit longer timing than the 900 cams but this should get you in the ballpark.Mains 230 to 250,pilot 30,needle jet Q2,needle 6FJ41 3rd notch from top,and slide 4.0 The Mikuni tuning book from Sudco is a big help as it gives the specs on different needles and the tuning ranges.I'm also running an open meg[boy it sounds good!] with no filters and due to the cam timing it is a bit soft on the bottom but once it climbs onto the cams about 5000 it really takes off. Oh yeah, the carbs are the TM41s your 750 will have no problems running that big a carb.

Bill


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 Post subject: Re: Wanted, the recomended jetting sizes for Mikuni TM41
PostPosted: Sun Dec 12, 2010 4:03 pm 
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Joined: Sun Nov 07, 2010 10:54 pm
Posts: 425
Location: Brisbane
Thanks Bill (s)

That gives me a good start.
Steve was saying that he had to change the float needle to stop the front overflowing?
Did you have the same problem?

graeme


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 Post subject: Re: Wanted, the recomended jetting sizes for Mikuni TM41
PostPosted: Mon Dec 13, 2010 12:43 am 
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Joined: Thu Oct 14, 2010 7:30 am
Posts: 138
I haven't had any issues with the 750 but I don't know which float valve is in it. 250 seems to ring a bell though.You do have to run the float level a bit lower on the horiz. cyl. but the measurement escapes me at the moment.When I had TM41s on my 900 it pissed like a racehorse but that had a fuel pump and I fell into a set of Keihin FCRs so I didn't look into fixing it.


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 Post subject: Re: Wanted, the recomended jetting sizes for Mikuni TM41
PostPosted: Mon Dec 13, 2010 8:08 am 
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Joined: Sun Aug 08, 2010 4:37 pm
Posts: 360
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Location: Ottawa, Ontario, The Great White North
graeme wrote:
Thanks Bill (s)

That gives me a good start.
Steve was saying that he had to change the float needle to stop the front overflowing?
Did you have the same problem?

graeme


Hey, Graeme:

I still haven't found my set-up file, but the float needle jet I used initially was a 200 recommended by Sudco. I later switched to a 190. Float levels were just about topped out. From memory, my main jet and needle/slide settings were the same as Bill's but the pilot was one size richer.

_________________
Steve Munro
loudbike
http://www.loudbike.com
http://www.vintagemotorcyclesforsale.com


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 Post subject: Re: Wanted, the recomended jetting sizes for Mikuni TM41
PostPosted: Tue Dec 14, 2010 5:39 pm 
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Joined: Sun Nov 07, 2010 10:54 pm
Posts: 425
Location: Brisbane
Thank you gents,
That will give me a good start.
Regards
graeme


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 Post subject: Re: Wanted, the recomended jetting sizes for Mikuni TM41
PostPosted: Tue Dec 14, 2010 11:43 pm 
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Joined: Mon Oct 04, 2010 7:47 am
Posts: 100
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Graeme,

I was hoping Steve would find his jetting file. The Mikuni TM41 are a good carb but the technology is more old two stroke design. I don't want to throw a wench in the works here but, I tend to jet mine a little different then Bill. These carbs work good at wide open throttle but small throttle openings can be challenging to jet for. I have had the best luck with the richer 6DP4 needle (which has different tapers) and leaner needle jets P-6 thru Q-0. For main jet you would probably be in the 220 range. I also use a smaller pilot jet 12.5 thru 15 and a slide is generally 3.5. I was using a vacuum fuel pump on the race bike with a 1.8 needle valve, but have ordered a 2.0 per Steve's recommendation. I have found that the motor setup has a lot of affect on how well these carbs work. On my race bike they always carbureted great and would idle fine. I had two different 750 motors in my street F1 with diffent cams and the TM carbs worked fair on the motor with some porting and two modified horizontal 800ss cams. On the small valve stock 750 motor I could not get the TMs to carbureted to my liking at all and I tried TM38s, TM39s, and the TM41 carbs and all the differnet needles, needle jets, slides, pilot jets, etc. With the race bike I never had any problems with the horizontal carb dripping but on the street bike it was always dripping no matter how I had it setup or which carbs. The only thing I could figure was with the race bike it was either on the rear stand or on the track were as the street F1 had a side stand that changed the angle the bike sat.

Since the TM41 carbs are popular for the F1 and TTs what jetting is everyone else using?

Palmer


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