XR650R Mikuni TM40 or Edelbrock?

[V-rider]

Originally Posted by RideFreak

Check the pump nozzle, Harley spec'd carbs usally come with a #70, that's going to be too big for the XRR. 45 or 50 is much closer to what you'll need.

Thanks - I actually took care of that already - got the #50.

[XRider]

Originally Posted by V-rider

Got the bike running. Just rode it on the street in front of my house for a second. Seems to run fine except the idle is too lean. Needs choke for a long time.

My idle mixture screw is turned out 3 turns and I tried some more on top of that - but still too lean.

I sprayed for vacuum leaks but didn't find anything obvious.

I thought I put a 20 pilot jet in, but I actually have a 22.5 in there.

My pilot air jet is a 1.2.

What do you guys think? I think I'll try my 25 pilot jet? I had an experience with my old Bandit 1200 that was similar. I put in too small of pilot jets and the idle became too lean. No amount of idle mixture screw would make up for it.

On the TM40 that comes in the Sudco kit there is a hose barb on the right side by the intake spigot that needs to be capped. You might check that the rubber vacuum cap is in good shape and not cracked.

The fuel screw should be between 1 and 3 turns out. Any more or less and means you've got the wrong pilot jet. You are doing this with the pump disconnected right? Also, you said the carb came off a Harley, are you sure it's not an HSR42 or 45?

I'm really surprised that the #20 pilot was too lean. I've done quite a few of these and always had the #20 or a #17.5 work.

[badcooky]

Actually Vrider the company sets them at 3.5 turns out and recommends this,not normal i know but it's their show.
These things can run a big main and a small pilot,hear me out dude.
Say normally a 20 pilot and a 135 main a 140 main will run a smaller pilot say 17.5.For real not making this up.
You don't have to believe me,but it's true.
Also with this carb when you do a main plug chop ya gotta stay flat for a bit longer than other carbs for some reason,till it clears out.
Weird but true dudes..

[XRider]

Running a smaller pilot with a bigger main makes perfect sence, I was just surprised that with a 140 main the 20 was too lean. About the fuel screw my information is different. I have the Mikuni Tunning Manual 4th edition and the section on tuning the TM40 says the fuel screw should be 1 to 3 turns out, less than 1 or more than 3 means you have the wrong pilot jet. However, I realize that these are just guide lines and not carved in stone. My hard and fast rule when it comes to tuning carbs is "what ever works".

[V-rider]

Xrider, I have the vacuum spigot on the side capped with a new tight cap. TM40 - no doubt about that. I connected the accel pump up to aim it at the needle last night and it is still connected. Of course it doesn't come into play at closed throttle and that is where my problem is.

I'm wondering about the condition of this used "Harley" carb... Maybe the slide is too worn and causing me problems at idle?

I guess I'll try the smaller pilot air jet or pilot jet tonight after work. There is no way I'll let it run this lean at idle. It WILL run - but it's not happy.

[RideFreak]

V-rider - the 1.2 pilot air jet should be right on the money unless you got some other mods, what does your airfilter look like (condition-wise)? What type filter are you running? I stick with stock filters (they're good), mine will pull enough of the airfilter oil out of it after a couple days of riding so it will get a little lean. I'm running a #20 at 5500' and it could probably stand to go a touch leaner but the fuel mixture screw is 2.5 turns out. Slight popping on decel and no popping back through the carb at idle which it did with too lean of a pilot jet.

[V-rider]

My bike has the "un-corked" intake manifold boot, K&N filter, plug out of the airbox, and two small triangles cut out of the cover with screen covering them. The exhaust is stock except for the insert - which I only "half" cut out to keep my neighbors happy. The bike probably doesn't even have 500mi on it yet so it is basically new.

Here is the carb rundown:

TM40
N100.604 #140 Main Jet
9DJY01 Jet Needle
568 Y-4 Needle Jet
VM28/486 #22.5 Pilot Jet
BS30/97 1.2 Air Jet
TM36/43-0.3 Accel pump nozzle (Sudco told me this was about the same as a #50 - it was the only one they had for the TM40)

I "glued" the intake and airbox adapters on with hardening brown silicone stuff and put a little set screw in each to make sure they didn't come loose, rotate, etc. I would be very surprised if I had a vacuum leak thru the intake adapter. (I did spray that also while it was idling and there was no change.)

And I also put a rebuild kit in it so I have all new soft parts.

I was disappointed about two things in the rebuild kit. One was the fit of the top cover gasket. I had to hold it in place to keep it straight while I tightened the screws because the little hole for the A/P stop screw was punched wrong. I wonder if the top cover isn't sealing well? Could I get a little extra air thru there if my slide is too worn? However, I did spray all around it while it was idling and nothing changed.

The other thing was no tiny o-ring for the idle mixture screw - dang! I had to squeeze a replacement that was a little too fat up in there. Hopefully that isn't causing me a problem.

Maybe I better check the pilot circuit again - maybe some crap broke loose and is plugging it up...

[XRider]

Having a slightly too large o-ring on the fuel screw shouldn't be a problem so long as it's tight around the screw. But I wouldn't make any assumptions until you pull the plug and see how she's burning.

[Hipster]

V Rider,

How did the 0.3 pump nozzle work out for you? I've always wanted a smaller nozzle and Sudco told me the 0.5 was the smallest available. Was the 0.3 a special order?

Originally Posted by V-rider

My bike has the "un-corked" intake manifold boot, K&N filter, plug out of the airbox, and two small triangles cut out of the cover with screen covering them. The exhaust is stock except for the insert - which I only "half" cut out to keep my neighbors happy. The bike probably doesn't even have 500mi on it yet so it is basically new.

Here is the carb rundown:

TM40
N100.604 #140 Main Jet
9DJY01 Jet Needle
568 Y-4 Needle Jet
VM28/486 #22.5 Pilot Jet
BS30/97 1.2 Air Jet
TM36/43-0.3 Accel pump nozzle (Sudco told me this was about the same as a #50 - it was the only one they had for the TM40)

I "glued" the intake and airbox adapters on with hardening brown silicone stuff and put a little set screw in each to make sure they didn't come loose, rotate, etc. I would be very surprised if I had a vacuum leak thru the intake adapter. (I did spray that also while it was idling and there was no change.)

And I also put a rebuild kit in it so I have all new soft parts.

I was disappointed about two things in the rebuild kit. One was the fit of the top cover gasket. I had to hold it in place to keep it straight while I tightened the screws because the little hole for the A/P stop screw was punched wrong. I wonder if the top cover isn't sealing well? Could I get a little extra air thru there if my slide is too worn? However, I did spray all around it while it was idling and nothing changed.

The other thing was no tiny o-ring for the idle mixture screw - dang! I had to squeeze a replacement that was a little too fat up in there. Hopefully that isn't causing me a problem.

Maybe I better check the pilot circuit again - maybe some crap broke loose and is plugging it up...

[V-rider]

Originally Posted by Hipster

V Rider,

How did the 0.3 pump nozzle work out for you? I've always wanted a smaller nozzle and Sudco told me the 0.5 was the smallest available. Was the 0.3 a special order?

I will let you know how well it works after I get a chance to ride it more. It's been raining hard all day here. Seemed to be good for the 30sec I rode yesterday.

I don't think it was special order... This is what is listed in their latest price sheet:
007.165 TM36/43-0.3 NOZ 5.51

I e-mailed Sudco and asked them about it (almost ordered the nozzle for the HSR42). Chad at Sudco said this is the one you want.

[V-rider]

The rain stopped for a minute so I went for a spin down the street after I put in the 25 pilot jet. Idles better now. I think it still could use more fuel so I will put in my 1.1 air jet some time and see how it runs. It is cold today so I need to run on a warmer day and see how good the idle gets.

I experienced the "pumper" effect - she just needed a extra squirt and the front wheel pops right up - even with my 15 tooth front sprocket. Woo hoo!

After I ride it more I will post again with more results.

[Hipster]

V Rider,

Thanks for the part number

[tarzan30]

Originally Posted by V-rider

The rain stopped for a minute so I went for a spin down the street after I put in the 25 pilot jet. Idles better now. I think it still could use more fuel so I will put in my 1.1 air jet some time and see how it runs. It is cold today so I need to run on a warmer day and see how good the idle gets.

I experienced the "pumper" effect - she just needed a extra squirt and the front wheel pops right up - even with my 15 tooth front sprocket. Woo hoo!

After I ride it more I will post again with more results.

I have the same effect with my eddie carb. i can be going 90km/55M and power up the front wheel in third with the 15CS sprocket! So much fun it makes me grin ear to ear

[badcooky]

The joys of a pumper carb.

[V-rider]

So I figured out why my idle was so lean - the intake adapter was leaking. I had to strategically spray one little spot until - vroomm - idled up smooth.

I thought that my permatex glue job (even heating it for a few hours in an oven until it was hard) would have been good. No luck.

So I did the J-B weld thing. Should be good now. I wonder what everyone else uses to seal those adapters with?

I hoping for a smooth idle now.