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XR650L XR650L Mikuni TM42-6, Whats Your Jetting?

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Hi, if anyone is running a Mikuni TM42-6 on their XR650L can you post what jetting your using giving the following info

Main Jet Size

Pilot Jet Size

Needle Number

Needle E Clip Position

Needle Jet Number

Pilot Air Screw Turns Out

Accelerator Pump Opening Position.

Altitude you ride at 

Let us know what you've got so we can get a definitive guide to what works well saving the time and expense for those who want to retrofit this fab carb.

 

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2 hours ago, Heo2 said:

Hi, if anyone is running a Mikuni TM42-6 on their XR650L can you post what jetting your using giving the following info

Main Jet Size

Pilot Jet Size

Needle Number

Needle E Clip Position

Needle Jet Number

Pilot Air Screw Turns Out

Accelerator Pump Opening Position.

Altitude you ride at 

Let us know what you've got so we can get a definitive guide to what works well saving the time and expense for those who want to retrofit this fab carb.

 

I have the TM40-6, I'm curious about the difference in performance if there is any. Using a 140 main at the moment. Bike is completely uncorked, FMF Powerbomb and DG muffler. Hot Cam stage 1. Altitude doesn't really affect these carbs much. Air box is desnorkled, covered up the holes I put in the side of it. Wasn't giving me much except for worse gas mileage using a larger main jet.

Edited by Beamer1001
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2 hours ago, Heo2 said:

Hi, if anyone is running a Mikuni TM42-6 on their XR650L can you post what jetting your using giving the following info

Main Jet Size

Pilot Jet Size

Needle Number

Needle E Clip Position

Needle Jet Number

Pilot Air Screw Turns Out

Accelerator Pump Opening Position.

Altitude you ride at 

Let us know what you've got so we can get a definitive guide to what works well saving the time and expense for those who want to retrofit this fab carb.

 

Here this may help...

 

Edited by EarthCruzn
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44 minutes ago, EarthCruzn said:

Here this may help...

 

I think they were jetting it way to high back then. Sounds like the tm40 is the way to go imo and cheaper. The AP works perfect with the settings from Niche. Same with pilot, you just have to figure out the best main and fuel mixture.

Edited by Beamer1001
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Pretty sure HSR42 is the same as TM42-6 which is what I have.

Bike has TwinAir filter, FMF powerbomb header and a homebrand straight through muffler, otherwise stock.

Tuning done with Innovate LC1 fuel/air analyser to make things easier. This is what I came up with.

Main Jet Size    #142.5

Pilot Jet Size      #20

Needle Number    #Y-97

Needle E Clip Position   1st clip

Needle Jet Number    #Y-4

Pilot Air Screw Turns Out  -  1.25 turns out

Accelerator Pump Opening Position. -  Start almost immediately off idle, Stop about 1/4 throttle (just below cruising throttle opening)

Altitude you ride at   - Sea level to 3000ft

Mileage   -    16.9 km/l  or 39mpg

Bike goes really well but looking forward to installing high comp piston and stage 1 hotcam.

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7 hours ago, greyrider said:

Pretty sure HSR42 is the same as TM42-6 which is what I have.

Bike has TwinAir filter, FMF powerbomb header and a homebrand straight through muffler, otherwise stock.

Tuning done with Innovate LC1 fuel/air analyser to make things easier. This is what I came up with.

Main Jet Size    #142.5

Pilot Jet Size      #20

Needle Number    #Y-97

Needle E Clip Position   1st clip

Needle Jet Number    #Y-4

Pilot Air Screw Turns Out  -  1.25 turns out

Accelerator Pump Opening Position. -  Start almost immediately off idle, Stop about 1/4 throttle (just below cruising throttle opening)

Altitude you ride at   - Sea level to 3000ft

Mileage   -    16.9 km/l  or 39mpg

Bike goes really well but looking forward to installing high comp piston and stage 1 hotcam.

The post earthcruzen put up from way back they were using 152.5.  No wonder they were having to disable the AP. I read there really is no performance difference in the 40 and 42.  Wasting money on the 42, the 40 works way better and way less hassle and gets better gas mileage. 😉😆

Edited by Beamer1001

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I'm sure there's not much between a 40 and 42 on a stock xrl.

Bike came with a brand new hsr42 still in the box, PO never installed it. Had to learn how to tune from scratch, approached it methodically but LC1 analyser made a big difference, no guessing. 

The milage I was quoting was from the first decent hit out since a rebuild, chasing 3 ktm riders around the nearby national park for six hours (one with the latest limited edition 790 adv r rally ...drooooool), on the throttle all day to keep up what a blast, wore out a set of brake pads too.

I do like the AP to get rid of the bog but found if it is still in play at normal cruising speed (about 1/4 throttle where I spent a lot of time commuting) the A/F ratio gets very rich no matter how steady I hold the throttle. I'm guessing vibration must cause fuel to be injected. No such problem if I adjust the AP to cut out just before that point. It's a compromise between having no bog and saving fuel.

Found the little spreadsheet I made up to compare needle jet/jet needle combos based on the annular area(things you do on a quiet nightshift). Reading back through my notes I went from  Y-6/Y-95  to Y-4/Y-95  to Y-4/Y-96  to  Y-4/Y-97  ,gradually leaner with multiple needle clip positions in between.

1810013958_tuninginfo.PNG.ddc5d616e8aad7a9fc7abaf4939141bc.PNG

 

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11 minutes ago, greyrider said:

I'm sure there's not much between a 40 and 42 on a stock xrl.

Bike came with a brand new hsr42 still in the box, PO never installed it. Had to learn how to tune from scratch, approached it methodically but LC1 analyser made a big difference, no guessing. 

The milage I was quoting was from the first decent hit out since a rebuild, chasing 3 ktm riders around the nearby national park for six hours (one with the latest limited edition 790 adv r rally ...drooooool), on the throttle all day to keep up what a blast, wore out a set of brake pads too.

I do like the AP to get rid of the bog but found if it is still in play at normal cruising speed (about 1/4 throttle where I spent a lot of time commuting) the A/F ratio gets very rich no matter how steady I hold the throttle. I'm guessing vibration must cause fuel to be injected. No such problem if I adjust the AP to cut out just before that point. It's a compromise between having no bog and saving fuel.

Found the little spreadsheet I made up to compare needle jet/jet needle combos based on the annular area(things you do on a quiet nightshift). Reading back through my notes I went from  Y-6/Y-95  to Y-4/Y-95  to Y-4/Y-96  to  Y-4/Y-97  ,gradually leaner with multiple needle clip positions in between.

1810013958_tuninginfo.PNG.ddc5d616e8aad7a9fc7abaf4939141bc.PNG

 

I don't think there's any difference in modded out xr650l's either. Only thing I haven't done yet is install my high compression cylinder and big bore jug.  I'm doing 0 to 60 in 4.5, let's race. 

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7 minutes ago, Beamer1001 said:

I don't think there's any difference in modded out xr650l's either. Only thing I haven't done yet is install my high compression cylinder and big bore jug.  I'm doing 0 to 60 in 4.5, let's race. 

Very happy with the current setup but I'm expecting another level with a high comp piston and stage 1 cam, and since I have it sitting on the shelf ...might as well use it.

Never thought to check 0 to 60 time ...will have to now lol

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23 hours ago, greyrider said:

Very happy with the current setup but I'm expecting another level with a high comp piston and stage 1 cam, and since I have it sitting on the shelf ...might as well use it.

Never thought to check 0 to 60 time ...will have to now lol

I do have the hot cam installed. Try the DR drag racing app. Very cool. Mines running great too. Since I have a spare piston and jug I don't mind running it hard, plus it's new. Might as well get some use out of it. Always tempted to go ahead and get it to it's maximum capability.

Edited by Beamer1001

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47 minutes ago, Beamer1001 said:

I do have the hot cam installed. Try the DR drag racing app. Very cool. Mines running great too. Since I have a spare piston and jug I don't mind running it hard, plus it's new. Might as well get some use out of it. Always tempted to go ahead and get it to it's maximum capability.

Neat little app, have to try it on weekend ha

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I agree that the 42 is probably overkill although I used it as i'm running the 102mm JE piston, stage 1 cam and flowed head, ram air filter and 2 x single headers into CRF250 mufflers (baffled)

My biggest fueling problem so far has been the AP, its got the correct 30 pump nozzle fitted and i've had to adjust the start position to just after 1/4 throttle opening so as to cure the absurdly rich issues at low rpm as i'm riding mostly on narrow mountain trails with alot of on-off throttle sections where the idle circuit alone is sufficient and then onto fast road sections.

Current jetting set-up is 142.5 main, 27.5 pilot, Y-6 needle jet, 97 needle on 3rd clip, idle screw 1 3/4 turns out, altitude is 0-1200 mtrs.

Still a little bit of work to be done but its a fantastic carb none the less.

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On 6/29/2020 at 4:16 PM, Beamer1001 said:

 I'm doing 0 to 60 in 4.5, let's race. 

0 to 60 in 6.2, 90 max, bring on the cam n high comp piston lol

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