Another TM40 Jetting Thread

So I rewrote my jetting notes last night so its a lot cleaner and easier to read.  Red boxes are what was changed. And I checked last night, my accelerator pump nozzle is in fact a 70 and aimed properly.  I've been running the carb without the accelerator pump rod for a while now.  I'm trying to put it in now and get my jetting set properly but have been having nothing but issues.

Full big gun exhaust
Opened airbox and side panel
Stage 1 hotcam
300 feet (~100 meters) elevation
65°F average temp
80% average humidity

PICTURE LINK



On Feb. 16 2014 (top right) after all my research I re-jetted pretty much everything to what seems to be a golden standard for the TM40.

But my bike ran so hot I was genuinely concerned damage to my engine would occur if I rode it.  A minute after starting my bike the headers were glowing red hot and the engine temp was soaring off the charts.  It did seem to rev and generally run okay though. (this was without the accelerator pump control rod)

I know my carb is clean.  I've taken it apart several times now and there's nothing in it but fuel.

I had a really bad experience with the accelerator pump rod a few weeks ago.  Pretty sure it was my end stop adjustment that I had totally screwed up.  I re-set the end stop and maxed out the starting adjustment last night and went for a little ride.  It is much better now.

I completely agree that I'm running really rich.
I completely accept I screwed up the accelerator pump rod stops originally.

I think I'm going to do drop my pilot back down to a 27.5 from a 37.5 with the rod.  In theory my bike will overheat and detonate if left at an idle (I really hate this).  But once you ride it the extra fuel from the accelerator pump should richen the bottom end and run great.  Right?

I'm almost starting to regret buying this carb.  What a pain in the  

BuRP, my main concern is running my bike lean and doing damage to the engine.

Something just crossed my mind , have you plugged/sealed the hole after taking the AP rod out before trying to jet the carb , as i think if there is a air leak somewhere it could affect the fueling and you will be unable to get the jetting right   

I'll look at that tonight when I re - jet again. But I don't think that there's any openings. The rod just pushes a plunger down which should be sealed up. I'll look at it real good tho and ensure there's nothing leaking there.

Its just an idea , i am not sure how its sealed ( i dont remember TBH ) , but leaving the rod in its place would be safer bet , you can back off the adjustment for the pump that it does not kick in as long as possible ( far enough to not affect the iddle circuit ) . Then everything stays sealed as it came from the factory , so the 27,5 or 25 pj might work .
I am not a carb expert but even i know that if you have to run 37,5 pj there is something seriously out of order , so make sure everything its assembled correctly and you have no air leaks .

Mad Frosty wrote:Its just an idea , i am not sure how its sealed ( i dont remember TBH ) , but leaving the rod  in its place would be safer bet , you can back off the adjustment  for the pump that it does not kick in  as long as possible ( far enough to not affect the iddle circuit ) . Then everything stays sealed as it came from the factory , so the 27,5 or 25 pj might work .
I am not a carb expert but even i know that if you have to run 37,5 pj  there is something seriously out of order , so make sure everything its assembled correctly and you have no air leaks .

You bring up a couple good points Frosty.  I'm pretty sure I could set the adjustments out enough so the rod is never actuated.  That would be really interesting to see how the 25 works with it set this way compared to removed completely.

The other part is an air leak.  What do you use to spray around the carb to see if you have an air leak?  Starting fluid? I don't want to set my bike or myself on fire, the shop is already messy enough as is  But the boot to the head and the carb could be leaking.  Its possible anyway.  Something I haven't really checked.

That's why I was reluctant to post my jetting.  The 37.5 PJ and 1.0 PAJ feels pretty good.  The bike doesn't run ridiculously rich.  It idles nice and runs strong.  But that's 5 pilot jet sizes larger (richer) and two pilot air jet sizes smaller (richer) than what's the standard and I don't know why.  Yet.
      rinse and repeat...

There have been some cases ( rare ) of the preinstaled adaptor leaking , might be a good idea to check it . ( brake cleaner ) .

Mad Frosty wrote:There have been some cases ( rare ) of the preinstaled adaptor  leaking , might be a good idea to check it . ( brake cleaner ) .

Excellent. I have lots of brake cleaner. Stay tuned   
  

"my main concern is running my bike lean and doing damage to the engine"

You got a bum right (well, a right & left one for that matter), and got some organ detecting de- & accelleration? Then you're good to go! "Lean" is only detrimental when WO (and this for a longinsh time) meaning the MJ, the rest you will feel and/or compensate for with the throttle (= also 'feel') as it either underperforms or is too rich.
However, 'too rich' is easier to do than too lean, simply because an engine is more forgiving there... hence aim to jet down!
The trick is to jet 'correct'.... so assume you're too rich, which statistically speaking is probably the case anyway.
Oh, too rich is also bad for the bike, but you know that ;-)

"have you plugged/sealed the hole after taking the AP rod out.."

No need to, no leaks here at all. Also, don't expect the timy rubber bellow to seal the rod airtight, it does not for it cannot.

"leaving the rod in its place would be safer bet"

Nope, bad idea, one can't adjust pumping away fully - and as said, the rod out does nothing but disabling the pump.

"brake cleaner"

You'd put that in the tank???
Me neither.... wave a gas burner (no flame, duh..) over the intake manifold rubber. If revs pick up bingo, a new rubber.
But, Master, call me silly (oh wait, you already have   ) but I did expect all & sundry to be in A1OK nick before you started jetting your carb, ditto for a shiny clean tank-inside, new fuel lines, filer etc etc, oh, airfilter too, no exhaust leaks, basically the whole rigmarole to be 100% for certain. Valve play, oil quality, new plug with set gap, it all plays a role.

37.5 IJ should not run at all I think, and you mentioning a 27.5 was 'awfully lean'..... makes me hunch Frosty is not mad at all, in fact he may well prove to be a clever Dick - is that your real name Frosty?   
Have fun finding what's wrong, and do try the 140 MJ also... you just might find a few horses more   

As per my habit (and no Dick, I'm not confused ) an additional post.
The last bit to 'jet' is the MJ, actually the easiest one. Find a testroad or -distance which is level, long enough (few km's), and ideally has a very slight uphill in it (not unlike the IJ testroute). Start at a marker and note the finish, and time your runs with the various jets. The shortest time indicates the best jet - which you can check then too, by means of a plugchop: from WO (an extended run, possibly top speed or at least a high speed!) close throttle & pull clutch & kill engine all in 1 go! Coast to a halt, remove plug and peek deep inside it.
The colour it has to have will vary with the fuel you use, no idea what shite you guys are flogged there but it will be different than our rubbish. Anyway, some brownish colour deep down the insulator nose, with lighter to very light brown/creme at the tip is a good 'general' description. Any black is too rich, any white is too lean. A good idea is to ask a local guru you trust, plug reading is best left to local experienced chaps quite frankly, but take a shot at it by all means.

So I pulled the carb and re-jetted nearly exactly as BuRP recommended.  I didn't take a picture of my notes but I'm fairly certain I'm running a bigger main jet (super easy to change).

PJ = 25
PAJ = 1.2
AFS = 3.25T
NJ = Y-4
JN = 9DJY1
NC = 3rd
MJ = 142.5
APN = 70
APS = ~1.5mm
APE = ~30%

Couple things. Probably should have been wearing ear plugs while reving my bike... 

You can adjust the rod stops so it does nothing.  I was running my little homemade remote fuel tank and was able to dial on the carb without the IMS tank.  If you set the Accelerator Pump Start properly then run the Accelerator Pump Stop out all the way they meet at exactly the same time and the rod does nothing.

So with that, it fired right up and ran horrible and didn't want to idle until I got the fuel screw set right.  It would idle okay then kind of stumble then cough out all of the sudden.  Finally got rid of that but my fuel screw is out 3-1/4 turns now.

Now that it was idling right and not coughing out, my engine temp was rapidly climbing and headers beginning to glow excessively.  So I started to back out the Accelerator Pump End stop allowing the rod to actually do something and it made a very noticeable difference to how it ran (off idle).  While reving the bike engine temps actually dropped and headers stopped glowing.

Once I hit this point I figured what the hell and spritzed the carb and boots down with brake clean.  I'm not worried about a little brake clean hurting anything.  I'd pour a little bit in my tank no problem, it wouldn't hurt anything.  I've used it to start engines plenty of times, but I got nothing out of it; no leaks.  I'll try the gas burner technique too.  I have a small torch that should do the trick.

After all that I figured screw it, put the tank and seat on then made a quick run around the hood between rain showers.  And it ran pretty good.  I tweaked on the Accelerator Pump Start a little bit and the fuel screw a little and it runs pretty sweet right now.  I can definitely feel a difference in acceleration.  Its crisp and instantaneous as you'd expect it to be.  I just wish it didn't run so damn hot.

~175°F to ~210°F were normal putting around the neighborhood engine temps.  That's not bad at all really but do a little stop and go clutch work and you're to 235° in no time at all and its climbing.  That is what I'm afraid of.  I've never seen my bike run that hot while just putting around before.  245° is the hottest I've ever had it. Ever. And that's getting really hot.  A lot of the riding we do is tight technical nasty stuff you pick through slowly so I'm worried and think I'm going to need a fan really soon.

Oh, and BuRP. I don't think you're silly.  I do however think the way you present your useful and appreciated feedback can be.  For example adjusting the rod to eliminate any pumping.  Your statement was incorrect.  You can completely adjust it away, I know for sure because I did it, its absolutely possible.  Its how bold and 100% certain you are in your statements that turn out inaccurate that make you look silly.  You're jetting feedback however, seems to be spot on.  Thank you.

 

You could try the 27,5 pj again ( few people run that size at sea level and colder climate but never seen anybody using bigger than that ) , the golden rule is "whatever works" .

Mad Frosty wrote:You could try the 27,5 pj again ( few people run that size  at sea level and colder climate  but never seen anybody using bigger than that ) ,  the golden rule is  "whatever works" .

I've thought about that.  But I decided against it because I am tuning in my driveway sitting at ~300ft but end up riding at ~2500 to ~5000 feet.  I think I'll even drop the 142.5 main tonight for a 140.  Tomorrow we ride in some pretty high elevations (3000 to 4500 feet)

I think a little lean at home will be fine.  I just need to be careful with trips to the coast

Keep the IJ 25 but drop the AJ to 1.1? The result is a slightly richer idle-mix...
I'd get the fueling absolutely spot-on for 'home' as this will give you a 'base-setting' from which to work (ie to lean down off, for higher altitudes). Glowing headers is wrong, ask me I've had them too. If that combo won't work I'd try the 27.5 but put the 1.2 back in... if that's too lean (I genuinely doubt it though) then the next step would be to put the 1.1 in, etc etc.
What filter you use bru? I hope now it is an oiled foam thing (TwinAir, UNI ot OEM, and a support screen must be present - either the std one or the XRsOnly-one with larger holes), not a cotton gauze (like K&N etc)... because a clean gauze will let more air past, concurrent with fines... until it has fouled up a bit (at which point it also starts to filter better).
I would have a good look at my mixture screw - no nicks/damages? O-ring (I think it has one) in good nick? In any case a tiny smear of copper-paste (copaslip, copper-ease or why) on the thread is a must, if not for lubing then for sealing it off.
Then your choke-mechanism: what have you got, a remote (cable) or a direct lever? In any case dismantle it and look if it seals perfect, however if it sucks 'false' air then waving gas over it (an off gasburner) will show this up.

Temperature: yes, this bike runs warm to hot when the going gets slow/technical, it's why many have a fan installed. With your large IMS this can't be done (at least not the 4" Spal puller) so beware of overheating, and a TrailTech Vapor (got temp reading + warning lights) I consider a must. Or duel core radiators which I now have, plenty capacity now.
This is a desert racer, designed for speed, and for this reason H did not install a pumper... it does not need one. But me & you put one up, in the process getting more power low down (ie at low speed) hence more heat must be shed... but the rads are small (racer, low weight, high speed etc) and the wind is minimal (low speed).
Yes, this bike can single-track, but do something to prevent overheating, especially so when a pumper is mounted.

So to make this more fun , i have been messing with my carbie today and i have messed it up    . It seems like the XR its a notorious carburation hypochonder .Gone from working setup to
Current mess -
PJ - 27,5
Needle 9DJY1 - the leanest needle you can get ( 4th clip )
Main jet 147,5
mixture fuel screw 1,5 turns out
I have fecked with the pump rod adjustments , delayed the begining of the sqirt and shortened the duration , now i am having little stumble /delay when fast opening the throttle and the bike apears to be running bit hotter , more confusingly the plug seems brownish not white and it pops on deceleration like the stocker used to do .( in a nutshel i am having both symptoms for lean and rich condition and have no idea what have i done , only the suspision that i have messed up the fuel pump settings and that affects how the bike reacts to the applyed throttle )

So the point of the story is - dont try to fix it if its not broken !!!

LOL! Noted. Thank gawd mines messed up then.  Honestly yesterday was pretty good. I've got some very minor things to tweak yet.

Frosty.
Your's never used to pop on deceleration?  Mine does all the time. I thought it was normal. It's not super loud backfiring but still it's popping. What you're saying is that this can be tuned away?

I'm pretty happy so far. Acceleration is pretty amazing. I think all I have left is to dial a bit on the AP start and stop. The start I dialed on a little bit and I think I have it delayed for to long. When I snap the throttle to 1/3 from closed I get a delay then boom, warp drive.  It was so damn cold yesterday that I adjusted it once (the wrong way) then never touched it again. Was to busy fighting off hypothermia in Mid June...

BuRP,
Thanks for the info it has really helped. I run a UNI foam with the high flow back and keep it clean and oiled regularly. I just installed the remote choke and everything there is mint condition.

As for the heat. Yesterday was 57°F on average and I was not dressed according. The bike however ran at about 170°F all day. Once in a while it spiked to 220 but it did that before too.

It starts extremely'er easy now  LOL, it was way better than OEM before, now its even easier yet! As long as you don't touch the throttle that is.

The only things I may play with right now are the AP stops the pilot air jet possibly and maybe the main. 140 may be a bit lean. Someday I may try the 142.5 again and see if I can tell a difference.

But as is its pretty impressive. A total panty drop'n, widow making wheelie machine. I'll have to get video of this elusive power wheelie nobody seems to be able to get. Mine does it with a good roll of the throttle in 1st and 2nd and with a quick on off in 3rd. 4th and 5th clutch up no problem with a little body English.

220F = 104C >> not hot actually, 240F is.
You have the higher-pressure redcap from XRsOnly? Increases the pressure from 1.2 to 1.6 bar, which helps boiling off too quick - and yes, it's one of the first things I bought. No, it does not help cooling but it does increase the thermal reserve, ditto their marginally cooler thermostat.
A thermostat starts opening at a given temp, ours at around 77C (76 XrsO's unit, 78 std unit).... then a gap starts appearing, and if the temp increases the gap becomes larger until fully open. I think it is fully open around 85C, which means this is the end of the modulation-span the thing is capable of - but don't confuse this as the temp above which the engine is running 'hot'.
Any liquid cooled engine with pressurized system may run to 230/240F without a problem, and a fan's thermoswitch typically should come On around 215Fthen.
An engine running low temps produces more power, one which runs warmer has a better efficiency >> hence no surprise that modern cars run the latter, and dragsters have no thermostat.
The coolant tank/reservoir acts as a thermal reserve, however be careful here. Boiled-off coolant is vented (as a vapour, quite a high energy content) through this liquid. The vapour is condensed here a bit but vents to the atmosphere, giving the engine a way to shed heat via venting through the radcap. Mind though, when this happens pockets of vapour, a gas, are present in the engine's cooling system, and these are not really capable of cooling like the liquid coolant is (they are but to a factor of around 2000 times less so!) so cooling becomes compromised.
The bottom line is, when your engine starts to boil stop, switch off and let it cool down until the boiling has stopped. You will also notice then that the higher level in the tank will get back to normal, as the vapours in the engine will contract to liquid again, and the cooling system will suck coolant into back into itself, this obviously coming from the tank.
But yeah, how do you know when it starts boiling when riding hmm? Pot luck most of the times, as one can't see the tank. A red light coming On helps a lot, hence the TT Vapor suggested.
Master, you're at sea level, high humidity and it's cold there... ie more air, and denser too. Some guys have reported to use the AJ 1.1, and you seem to have the 1.0 even - try them? I know I would, and obviously the 1.0 will get more petrol out of the 25 IJ than the 1.2 will.
Oh, yip, with a small AJ the needle comes 'On' (or: in effect) a bit earlier, pls know it (In theory this could mean using a 'leaner' needle but set higher than 'mid' by means of the clip!).

Madder, why did you put in a way-off jetting population???? I mean, I presume yours was running fine? Oh well, yes, you may   

Fwiw, my jetting list I got to from fiddling, however based on info I found on the net... which turned out to be very close. I bought a whole heap of jets/needles to play with, and tried a lot of combinations. If ever I will find the time to go to a dyno I will try to find the optimal needle, however it may be that the one presently in there is the best one, it certainly feels like it to me. Oh, yes, the needle it the most tricky part of the lot, and arguably also the most used one as we all (I think?) ride in the band where it works... so yes, I'm a sissy, I don't ride WO everywhere  

"Frosty.
Your's never used to pop on deceleration? Mine does all the time. I thought it was normal. It's not super loud backfiring but still it's popping. What you're saying is that this can be tuned away?"

Yes it used to a lot when i had the OEM exhaust with HRC tip , but it dissapeared with the new FMF Q4 , now its back   

The main reason why i have started the tuning again was that efter the valves have been adjusted the bike started to run little bit rough and after something like half a minute it coughed and died , so i went to fix it and obviously made it worse   
It runs now and the local kids love the " racing firebreathing beast " sound but i dont think its good for the engine . I had the AP set perfect before and the responce of the engine was instant and crisp now there is a small delay which would be fine actualy if i never experienced the " perfect " setting , now i want it back because once you try the pumperoin you will get hooked forever   
I really like this carb but i have to say its quite complicated one to dial to perfection as everything you change affects the whole system , it takes loads of time to find the perfect combination of jets and settings . I think i was just lucky when i did the first setup and hit it pretty much spot on , the luck had ran out now and i lack in the experience department in tuning carbs , saying that i know loads more than i ever knew before the XR entered my garage .