Sumotrack rebuild

Are you running an AFR sensor?

Ok, the topham style tm34 carbs need a small pilot jet. They come with a 20, I dropped to a 17.5 and it's still rich, so I'm going to try going up on the pilot airjet(don't want to pull the floatbowls again). The needle jet is a little lean so I have a 1 size up coming. Main jet seems good in the mid 12s @70*. Jet needle also seems fine.

In other news I finally fixed my slight oil leak. It was the pushrod seal leaking due to a worn bushing. Didn't want to order a bushing so I made my own with some bearing bronze I had. Now no more drip after running at higher RPM.
 
Are you running an AFR sensor?

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QUOTE="Ratranger, post: 860531, member: 26571"]
Ok, the topham style tm34 carbs need a small pilot jet. They come with a 20, I dropped to a 17.5 and it's still rich, so I'm going to try going up on the pilot airjet(don't want to pull the floatbowls again). The needle jet is a little lean so I have a 1 size up coming. Main jet seems good in the mid 12s @70*. Jet needle also seems fine.

In other news I finally fixed my slight oil leak. It was the pushrod seal leaking due to a worn bushing. Didn't want to order a bushing so I made my own with some bearing bronze I had. Now no more drip after running at higher RPM.
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Yeah, I'm using the zeitronix zt2 I have. I went ahead and got a gauge for it, so I've been watching it.
 
Yeah, I'm using the zeitronix zt2 I have. I went ahead and got a gauge for it, so I've been watching it.
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Amazing how it is possible to see everything that is going on with jetting, reversion, once the sensor is installed
 
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Yeah, I'm using the zeitronix zt2 I have. I went ahead and got a gauge for it, so I've been watching it.


Amazing how it is possible to see everything that is going on with jetting, reversion, once the sensor is installed
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It's amazing to me how a bike can fell pretty good while being pretty far off of ideal or even good jetting. A few jet changes and the vibration at 50mph is gone, idle is smoother and more consistant, bike pulls better everywhere. It's on the lean side around 1/8-1/4 throttle cruise, still rich at idle, 1/2 throttle cruise is good.

A wideband just takes all the guess work out of jetting. Reading plugs is unreliable with modern fuels and the charts in haynes or chiltons manuals oversimplifies it. The butt dyno is also notoriously unreliable, often just agreeing with what you want to be true.
 
Amazing how it is possible to see everything that is going on with jetting, reversion, once the sensor is installed
It's amazing to me how a bike can fell pretty good while being pretty far off of ideal or even good jetting. A few jet changes and the vibration at 50mph is gone, idle is smoother and more consistant, bike pulls better everywhere. It's on the lean side around 1/8-1/4 throttle cruise, still rich at idle, 1/2 throttle cruise is good.

A wideband just takes all the guess work out of jetting. Reading plugs is unreliable with modern fuels and the charts in haynes or chiltons manuals oversimplifies it. The butt dyno is also notoriously unreliable, often just agreeing with what you want to be true.
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I second every word you said. After completing my build, the bike ran fine, or so i thought. Then after break in, on the dyno it showed no improvement over stock and massive reversion in mid range. The plugs looked ok, etc. Then with every change and a subsequent trip to the dyno, there was always something major to improve. After paying for something like five AFR guages in dyno fees, I installed my Innovate and was done with adjustments in a week. The bike was transformed. I still see an area I can improve, that I would not have known about had it not been for tha gauage, but that will need the header redesign. Should have installed the AFR guage from the beginning.
 
Really makes you wonder how much power or fuel economy gets left on the table sometimes. It's also surprising how much each area can be fine tuned with carbs like the mikuni RS or the keihin FCR. Although I do like the way the mikuni uses the needle jet/emulsion tube to tune the 1/8-1/4 throttle range rather than just the needle. It gives a little more control with less compromise compared to the needle only on the FCR.
 
Really makes you wonder how much power or fuel economy gets left on the table sometimes. It's also surprising how much each area can be fine tuned with carbs like the mikuni RS or the keihin FCR. Although I do like the way the mikuni uses the needle jet/emulsion tube to tune the 1/8-1/4 throttle range rather than just the needle. It gives a little more control with less compromise compared to the needle only on the FCR.
FCR is the Cadillac if your used to tuning them, the closest thing to fuel injection for power and response.
 
FCR is the Cadillac if your used to tuning them, the closest thing to fuel injection for power and response.
I have had 2 FCR carbs on my DRZ, 1st a 39, and now a 41. Using only the needle for 1/8-3/4 throttle makes it a bit of a compromise. It was getting terrible mileage with standard needles, so I had to switch tothe taffy super needle. Once that was set so I could get decent mileage I had to go way bigger on the main to keep it from going lean.
The mikuni flatslide pumpers have a better setup using the needle jet for low throttle and the needle for higher throttle making less of a compromise.

In the end both are good, they tune a bit different, but it's down to preference and space. Both are also better than a smart carb or lectron for overall tuneability.
 
I decided to try an experiment today. The bike runs great, but feels soft below 3500rpm or so. So I got a pair of cheap amazon velocity stacks to test. I warmed the bike up with the filters on, then swapped the stacks on. The bike not only felt like it picked some up below 3500, but it felt like it pulled harder above there too. So my next step is to modify the stacks to take a filter. I will notshortenthe engines life toget a little more pep.
20241031_113608.jpg
 
With the w/r, what a/f are you targeting at WOT?
At p/t what a/f are being targeted?

If you have any questions on what I am speaking of, then..................................

c
 
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