APT SmartCarb

[forgiven]

Seen two problems with the summary...I believe the check valves that will be in the cast will eliminate the overflow issue, and even with the 38 we should see more bottom end as well as top end.

[modifier]

Originally Posted by forgiven

Seen two problems with the summary...I believe the check valves that will be in the cast will eliminate the overflow issue, and even with the 38 we should see more bottom end as well as top end.

Maybe that is their solution at this point. When I wrote the summary, about a month and a half ago, there was no mention of check valves. Glad they figured something out.

On the 38 vs 36mm, I was just repeating what they told me at SC. But they also said that a 38 should work fine. KTM 250/300s come with 36s these days. But my 04SX motor came with a 39mm. No stumbling off idle.

Flying Bob, since a float works by floating and needs to have the fuel at least somewhat level, how did adjusting them make it stop flow when everything was 90 degrees from horizontal? Gravity maybe?

[nambo-trev]

Originally Posted by modifier

Maybe that is their solution at this point. When I wrote the summary, about a month and a half ago, there was no mention of check valves. Glad they figured something out.

On the 38 vs 36mm, I was just repeating what they told me at SC. But they also said that a 38 should work fine. KTM 250/300s come with 36s these days. But my 04SX motor came with a 39mm. No stumbling off idle.

Flying Bob, since a float works by floating and needs to have the fuel at least somewhat level, how did adjusting them make it stop flow when everything was 90 degrees from horizontal? Gravity maybe?

I asked about the flooding when this thread first started and Corey had told us about the addition of check valves to the next batch of billet and cast. That is why a lot of us have waited

[Flying Bob]

Originally Posted by modifier

Maybe that is their solution at this point. When I wrote the summary, about a month and a half ago, there was no mention of check valves. Glad they figured something out.

On the 38 vs 36mm, I was just repeating what they told me at SC. But they also said that a 38 should work fine. KTM 250/300s come with 36s these days. But my 04SX motor came with a 39mm. No stumbling off idle.

Flying Bob, since a float works by floating and needs to have the fuel at least somewhat level, how did adjusting them make it stop flow when everything was 90 degrees from horizontal? Gravity maybe?

Don't know how to answer that particular question. I didn't check the floats after unpacking the carb and installing it on the bike. I had cable retainer issues with the disk rotating until I put a pin in the unused locating hole designed for a screw. I had the flooding issues when the bike ended up on it's side, and on extreme downhill (nearly vertical) drops in races. I communicated with Corey about the check valve fix, and in those discussions, he suggested the I check the float level as during APT's testing they never had the extreme flooding I described. When I pulled the carb and the float bowl, the tangs appeared to be level, maybe slightly low (upside down equaling higher fuel level). While bending the center tang, I noticed one outer tang did not have any 'wear/contact' indications. I set the tangs slightly beyond level for a lesser bowl volume, made sure the float pins were properly positioned and filled the carb with fuel while holding it vertical. Then I removed the float bowl while holding it without letting fuel spill, and measured the level of the fuel remaining. It was approximately 3/4 full. Corey earlier suggested 1/2 to 3/4 full, so I reset the level again to reduce the volume a little more. It's set at approximately 5/8 full. Put it on, fired right up and raced the next day. Definitely hit the dirt a few times, and the bike just kept idling without any suggestion of dying. In my case, I am assuming the one float was on the wrong side of the tang and interfered with the needle valve thereby allowing gas to flow freely. Bike has always run superbly with the SmartCarb other than that.

[modifier]

Originally Posted by nambo-trev

I asked about the flooding when this thread first started and Corey had told us about the addition of check valves to the next batch of billet and cast. That is why a lot of us have waited

Hmm? Don't know what to say about that. When I spoke with him and on several posts at Ktmtalk a month ago he said they didn't have a solution yet. I suggested trying some kind of vacuum activated valve and he said that was along the lines they were thinking. All that was way into the two threads.

Maybe the GG forum was given secret information that the KTM forum was not

[Corey]

Originally Posted by GMP

Is the metering rod adjuster in the top of the carb sealed with an oring? Just thought about that.

Yes, o-ringed and taper seat.

[Corey]

Originally Posted by nambo-trev

I asked about the flooding when this thread first started and Corey had told us about the addition of check valves to the next batch of billet and cast. That is why a lot of us have waited

I believe the wait is worth it.

The prototype overflow valves are working very well and provide a nearly fully contained fuel system, which is pretty cool for a carburetor. Here's what testing has showed so far:

In the event the floats stick open, the check valves shut the vent lines immediately and then the only fuel that can enter the engine is through the nozzle (jet size orifice throttle shut) and is a 97% reduction in fuel flow compared to the vents being open. We've been toying with the idea of reviving Grose Jet fuel inlet valve technology (if permissible as no one seems to building them) it's a lot like our overflow valves in technology and would be a good fit. Likely then any float leaking issues would be vastly diminished.

The overflows are very fast reacting valves, so little to no fuel can enter the engine during a tip over, roll over or upside down; the bike can be dropped and will continue to run indefinitely, depending on angle, if over center far enough to shut the floats then it will run until the bowl runs dry. If upside down it will quit running because the nozzle is no longer in the fuel. A full on crash we haven't accomplished just yet, but give me time....

http://www.flickr.com/photos/8954608...in/photostream

Once the bike is dropped and lays there long enough to die it will start easily in one or two kicks, usually without opening the throttle, clears up easily and your off and rocking.

A couple of things we have to do yet. Several retro fit billets are going to our GasGas racers for review and altitude testing, patent paperwork/submission and a little better parts pricing search. This should all come together about the same time the new billets show up at the end of the month. We're now really close guys and there will be a retro-fit version for our existing billets, a slightly different (shorter) version for the new billets and finally the valves will be fully incorporated into the float area on the cast versions.

BTW the cast carbs are coming along nicely too and different sizes may become available sooner if our new vendor works out. Corey

[john01]

Sounds good to me . Thanks for the follow up report.

[nambo-trev]

That's what I'm talking about! Now I'm pumped and it will be worth the wait for sure!

[john01]

Oh they are well worth the wait . Really having a ball riding my 165 Husky with the SmartCarb. So much smoother and more responsive; unreal.