Only member that has TM AFR data backing up his main jet selection is PWJM.. You'll need to get his best opinion... Send him a PM if he doesn't show up here soon..

 

Oh, I forgot Richard Avatar.. He also has done AFR meter testing on several TM's..

 

I would like to know if Bill Blue has the correct recipe for setting up his carb on your bike. This isn't rocket surgery, and he should at least have data that allows a for a near perfect setup..

The only way you'll know your bike is fueled correctly, with the charts to prove it, is with a dyno run..

 

Yes he was pretty adamant not to mess around with the jet needle and airbox, and this was just a case of it probably running too rich or too lean. So that tells me he's done a fair bit of testing. (apart from removing the airbox for testing)

Just change down to a 140main jet is his recommendation. He said he'd put a 142.5 in there. I also asked him what about trying a 130, and he was NO !!! you'll run too lean and damage the engine.

All my problems fit in line with it running too rich. Well for starters there's the sooty plug.

The bike runs better cold, and runs better with only slight throttle. Plus i was burning thru a tank of gas far quicker than expected. I should be able to get around 75 on a 351, not 55 on a tank. Stock 250 i was able to get around 85. Of course riding styles need to be taken into consideration. the one disadvantage of the pumper is if you're someone who likes blipping the throttle, you're going to burn thru gas a lot quicker, as that pumper will really pump fuel into that new 351 cylinder.

I think Bill did his best on a pre-tune of the carb based on experience. But with me being at sea level, he just got the main jet a little too big.

Thanks for that spreadsheet. Once i'm running sweet, i'll update with my settings.

 

Mine also has the 351 and Pumper with a 142.5 in it modified by Bill and had similar symptoms at first. Swapped out stock snorkel for KDX one and runs great now. I see you have a slip on so you may be able to remove the snorkel or lid if you haven't already tried that.

 

Thanks, i've gone ahead and ordered a 140, 137.5 and a 135 main jet.

Jets are only $6 a pop, but shipping was $8, so for the sake of an extra $12, i thought we'll at least i have room to play with if the 140 doesn't work out.

I know the 142.5 is too rich at sea-level... Yes could probably remove the airbox lid or upgrade the snorkel, but running costs would still remain higher than what they could be with the bigger jet, as far as i'm understanding things.

(still learning jetting)

 

It's important to remember that at sea level you're actually getting MORE air than you otherwise would. So if Bill put in a 140 at his elevation (assuming higher than sea level), you'd be running leaner than him (albeit only slightly).

As for running without the airbox lid or a bigger snorkel, operating costs might be marginally impacted, but if you're getting a proper mixture of air and fuel you're likely to get more bang for your buck on every stroke, so you won't need to use as much gas in the first place. You're correct still of course, you will use more fuel as you are creating the potential to supply more fuel but it's still something you can control with the throttle.

If you're running the stock snorkel on a 351 you're certainly going to be overfueling. I remember a few threads back where of people who are running 130 main jets on their TM36-68's with an upgrade snorkel. The bigger piston pulls more air and increases the vacuum on the needle jet & main jet. To put that into perspective, on my TM on a stock 250 bore, I'm running a 132.5 for optimal top end fueling.

I'm not sure how the 33-34 flows though, I would think the smaller bore would increase air velocity and therefore also increase the draw of fuel through the needle jet.

It's really tough to say without at least trying some smaller jets. I have doubts that running the bike lean for 10 minutes will do any damage. The Stock Trim was so lean it barely started on cold days.

 

142.5 seems about right for me at 150ft above sea level even with stock exhaust (next years mod) Same symptoms until snorkle was swapped. You could try removing snorkle and duct taping hole to different sizes prior to changing jets as I know how much fun it is pulling that carb! Good luck.

 

I removed the lid, and ran it up and down the road. It ran 100x better. Actually almost lifting the front wheel, and no holding back until i get to about 9k which may just be the characteristic of the 351.

Eitherway i do have my jets on order and they'll be here in a few days. I'll definitely goto 140, and go from there. Would be nice to get around 75miles to the tank.

Yes not looking forward to pulling that carb. She's somewhat bigger and less managable than the stock CVK

 

Out of interest what mileage are you getting from a full tank on the 142.5 ?