Triumphrat

BadMouth · 04-15-2007

Finally got my dyno results. Not bad I guess, except for the screwey fuel mixture, but not all that I had hoped for.

The really horrible "off the chart rich, then dangerous lean" line is the initial run (142.5 mains, factory pro needles on center notch) I had moved the needles up just before dropping it off. I should have left them alone. The better one is after they tuned it - 127.5 mains(if I heard/remember right, maybe 137), needles lowered/shimmed & stiffer springs on the slides.

The current setup also includes D&D 3 into 3's, 955 sprint cams, and K&N in the factory airbox with almost the entire back hacked out of it. My rev limiter is also apparently at 8800 rpm (I told them to hit it :-D ).

Any guesses as to why I'm going lean at high RPMs? Seems odd that it's in a safer range after they put smaller jets in it.
Are the stiffer springs killing my throttle response (feels like it). I've cleaned the paint chips out of the tank. Could the factory filter not be flowing enough fuel? Could this result from me botching the valve clearances (first time I've done it). When I run it full throttle from a stop, it seems to die (like it's fuel starved) when it hits around 8k.

Hoping to get some advice. I think my next move is the Thunderbike exhaust. Maybe the added backpressure will keep it from going lean and shift some of the torque back to the lower rpms anyway (at least that's my dream result).

[ This message was edited by: BadMouth on 2007-04-15 12:13 ]

jimmyj900 · 04-15-2007

Lean mixtures don't affect power as much as rich mixtures do and you won't get lean misifres until you hit the 18-20:1 air:fuel range, so don't worry too much about that. If you can't get the lean mixture down, then run premium gasoline to prevent detonation.

The wet bottom end can be several things -- too small straight diameter on the needles, needles set too high, oversize pilot jet, oversize slide port.

Are you using the stock needles or the DynoJet needles? If you've got the DynoJet needles, then go back to stock and see how it runs. The stock needles are stamped 5E1. (Also if you've got the DJ needles then the slides have probably been drilled to open the slides faster.)

If you've got the stock needles, check the pilot jet size. Stock is #40 on the Mikunis and I wouldn't go too much over that. If the pilots are bigger than about #42 then replace them and see if that gets rid of some of the bottom end richness.

With stiffer springs the needle taper will kick in later and I suspect that's why you've got the rich spot at 5700 rpm rather than the usual 4500-5000 rpm.

Jim

BadMouth · 04-15-2007

Thanks Jim. I was hoping to get your opinion.

It's a 2000 TB. I'm running factory pro needles in Keihins, I should have mentioned that. I have 42 mains in it right now. I do have some 40's I can drop back in. The slides haven't been drilled, as I'm the only one who's monkeyed with it.

I'm riding down to sea level next month, so I'll wait until I get back before leaning it out.

It does look like the needles need to come down. I'm curious as to whether the dyno shop had a run where they were down too far (this only shows the first and last run). They said they had the carbs off 4 or 5 times, so I'm assuming there were other runs in between. They also said they shimmed the needles. I assumed that meant that one clip position was too high and the next was too low. Maybe they just misspoke and meant that they moved the clip.

I still need to figure out why it's missing at 8k. I just got my speed triple igniter working, so I'll have some more room between the miss and the rev limit. Weather sucks too bad to venture out today (had to ride home in sleet last night).

[ This message was edited by: BadMouth on 2007-04-15 15:03 ]

jimmyj900 · 04-15-2007

Quote:

It's a 2000 TB. I'm running factory pro needles in Keihins, I should have mentioned that.

KEIHINS! Big difference... :-D

You might want to try the stock needles with a 1/2 mm shim and the #40 pilots and see how it feels. The FP needles have a faster taper than the stock ones and that could account for the rich spot.

Jim

jimmyj900 · 04-16-2007

If your pilot jets are over #40 they're too big.

Try the stock needles instead of the FP needles with the same main jet. The slower taper on the stock needles will lean the mixture out a bit on the bottom end and might put that area in range.

See how that feels and then try another dyno run. The problem your dyno guys have is that they're pretty much stuck with the needles and slide mods you've done, so they've done their best with what they had to work with.

Jim

ecrabbit96 · 04-16-2007

Moto touches on one aspect of carb tuning that most don't think about. Float level.. I agree Jimmyj900 the pilot should probably be the 40 at most. The needle for the mains, raise to rich, lower to lean. The float level comes into play when we start talking about demand. If the foat level is stock with all the other mods done, then the result may be lean because the bowls do not have enough fuel ready for the demand of WOT. You are now pulling fuel at a much faster rate and yes it will replace it self but having a higher float level offers more available keeping the straws submerged under heavy demand. At WOT the needles are out and the mains are wide open. My thoughts, rich on bottom, pilot too big.. lean at WOT, not enough fuel available to support demand. Raise your float levels 3-6mm.

ecrabbit96 · 04-16-2007

Well I would start by saying, If you start with a stock bike having #38 pilots and the a/f ratio is good, then you add an air filter cams and what ever to increase flow you should end up lean. Add #42 pilots and you are rich, wha la, too big. Also too consider, if the needles are too high in the mains, then you will pull fuel through them even though you are not calling for it at idle. If you dont correct these issues then yes raising the float levels will make it worse, get the pilots right and the main jet needle height right and I think you will find that raising the fuel level in the carbs will help the lean top end. I believe that you are supposed to get WOT working well first, and adjust your mid range next (needle height), and then worry about final pilot settings. I still think #40. No evidence, personal experience. 127.5 mains seems hugh to me as well.
If this were my bike, 105 main with clip on second from the top, #40 pilot starting with 2 turns on the screw, raise float level 1-2mm. Good start point, tune from here.

BadMouth · 04-16-2007

*****! I forgot to mention something! (prepares for beating).
One of the carb rubbers was sucking air during the initial run and that was the cause of it going lean at high RPM. I'm not sure why it slipped my mind. All apologies.

The float height was set at 17.5mm when I installed the FP needles (long before the cams & airbox hack).

ecrabbit - I had 105's with the restrictive stock airbox, but I hacked almost the entire back end out of mine. Between that and the D&D's, I'm flowing a lot more air now.

I was trying to copy Saigon5's setup somewhat, so I could get it dialed in easier without having to reinvent the wheel. He's also got the torque curve that I'd like to get to. I didn't think about the possibility that he had kuni carbs. Here is that thread Clicky Am I handicapped by the Keihins?

Thanks for the replies and discussion. I'll make a few changes until it feels good on the butt-dyno, then take her back. The factory needles don't taper much and look thicker, so they may be the way to go. (and I can get a little upgrade money by selling the titanium FP ones)

I tend to cruise wherever the torque is, so I'd like to get it shifted back down to a lower RPM.

jimmyj900 · 04-16-2007

OK, I'm out of here.

Moto is now the 'expert' and maybe he'll even get a Triumph some day.

Jim

ecrabbit96 · 04-16-2007

The factory calls for about 1-1.5mm above the seam where the bowl attaches. The over all depth is 12-15mm, sounds like your levels are about where they should be. The carbs will only effectively draw so much air pressure. I think, (opinion) that 127.5 is more jet then the carb can support. Putting the fatter needle in will bring that down for idle and mids still giving a hugh spout for WOT, if the carb can support it. I would more consider bringing the main down more and using the more slender adjustable needle. Cool that you found the air leak in the carb boots, that should change things for the better.