APT SmartCarb

[drehwurm]

I've got my parts from APT including the new R080 rod and a new slide return spring - spring is way better the original one and works flawless. New bike is also in the house, a 2014 250 2-stroke which will be transformed into a 300 later (except if I like the 250 displacement). SC with the R080 is already on the new bike and feels very different, at least in the garage, than before. Where I could whack the throttle open without hesitation on the 300 with the A100 rod at 75 clicks out, the 250 (well it's a new engine that needs to be broken in) will bog heavily with the R080 rod at 65 clicks out. Hope to get my maiden ride tomorrow.

FWIW regarding the floats - by now I have meticulously polished every sliding surface including the sidewalls of the float bowl where the floats can touch. So far it looks like I haven gotten rid of any inconsistencies possibly caused by the float system and I can now leave the petcock on for any amount of time without flooding the engine; couldn't do that before.

Michael

[Jakobi]

Look forward to hearing your feedback once you get some time on it Michael.

Corey, originally you advised that the carbs had a small break in period where their performance improved. Was this related to the metering rod itself? or other components within the carb?

Changing from the original needle (A100 I think) to the R080 I noticed an improvement off the bottom end where my orginal would bog quite heavily when cracking the throttle. The R080 feels a bit crisper through the mid too. Very aggressive when on the pipe. Hard to guage performance still as last ride out it was very wet and I spent a lot of time short shifting. It still seems a little inconsistant at times too. Weather its the MR breaking in, or the floats changing position, I'm not sure.. but its definitely changing its characteristics from when I first dialled it in, to during the ride, and even again after a small warm up ride after washing the bike. I'm looking forward to putting some more kms on mine too.

[john01]

I have my fingers crossed for you and hope you get it dialed in. Mine has worked like a champ since day one testing in a cold rain. I do like the fact that you haven't given up on the SC. Good luck Jakobi.

[forgiven]

Surprised no one mentioned but APT says that they are on target for August 12th release with good results.

[drehwurm]

Well, today I got the first ride on the new 250, stock engine, and the SC with the R080 metering rod. In short, if the SC would have performed like that from the beginning on, it would have been much more a love affair than the love/hate relationship it has been.

The magic word today was consistency! It was consistent in tuning and performance where as delivered it was like a moving target. Started out with 65 clicks, but this was way too lean and I kept going in 2 clicks (richer) each lap. Took me a lot of laps - I'm now around 50 clicks out! Tuning was easy though. Ride - feels lean, whack the throttle - bog, crisp idle/off idle - it's still lean. 2 clicks in, go again. Then suddenly, clear as an Austrian mountain stream, the idle/off idle gets a little "burbly", the bog when whacking the throttle is gone and the bike starts to pull as expected - BINGO. Not even a hint of spooge. Bike ran fine for the rest of the day with no changes.

So what did I learn today:

.) I'm missing the 300 the 250 is ok, but the 300 is it for me! Can't wait to get my 300 kit.

.) If you want to run the SC, you have to live with the slightly burbly idle area. It is what it is.

.) I don't trust it yet - maybe it is the modified heads (optimal squish, bit higher compression) that cause problems with the SC since most people that have problems don't run stock engines. I will cut the stock 250 head to optimize the squish band to see if it makes a difference with the SC. Then the 300 kit will go on in the same configuration I was experiencing troubles with the SC and A100 MR. If it sill runs fine then I'll officially be happy

Michael

[andoman]

Glad to learn of successes coming from those that experienced frustration.
But this news has me wondering:
Since I'm not a jetting guru, am I getting all the performance that I could be getting? Put another way, Is "much better than AS-II" performance with my A100 MR not as good as I could be getting with an A-80MR?
Hmmmmm.....

[Jakobi]

Good points and a welcome update Michael.

I wonder if you are correct with the engine mods. It'll be good to see how the configuration reacts to your modifications as you make them. I'm looking forward to those updates. You may find modding the head will help you enjoy the 250 a bit more too.

I also agree with the comment re the burbling. Some has always been necessary off the bottom end, but it seems the smart carb gets you to deal with a little more than normal. Every time I've tried to clean it up there is as very noticeable flatness that makes its way into the rev range and you notice the torque sign off. Enriching it up the burbles come back, but so does the grunt. Finding a happy medium is the challenge.

Strangely, I noticed some changes in the way my R080 ran, from the first run through to where it is now. That very first ride on the R080 had me over the moon. The next ride I started to experience the burbles increase more, and had to start leaning it off more. More seat time required.

Michael, any pictures of the parts you polished internally?

Corey, where are the updates with the grose valve? Are you looking at rolling them out?

[rosco]

Michael, What brand 2014 250 2t did you get?

[Jakobi]

I just got a friendly reminder why to not test on the stand.. Started it up and it ran lean and raced at idle a bit. After it warmed up and settled a bit it still hung after a light ride up the street. Basically went back a bit richer again to the point where it felt best. One click more and it went fluffy. One click back and it felt good again. Now to test it in the field tomorrow! Going to catch up for a ride with Gas Monkey while he's here in Aus.

[drehwurm]

Originally Posted by Jakobi

Strangely, I noticed some changes in the way my R080 ran, from the first run through to where it is now. That very first ride on the R080 had me over the moon. The next ride I started to experience the burbles increase more, and had to start leaning it off more. More seat time required.

Michael, any pictures of the parts you polished internally?

Yes, the change in performance every ride has been driving me crazy also, but I hope that is finally gone now - we will see.

Unfortunately I lost my camera a month ago in the Greek mountains and not being a member of the smartphone generation I'd need to borrow something to make photos.

I started petty much right away when I got the SC with taking out the float needle seat and needle and started polishing/lapping those parts as I had the impression that the needle would not slide freely in the seat. Next was the "forked" part which had some sharp edges where I thought the floats could "catch". Also polished the part where the pins of the floats slide on the fork and where the float needle touches. Last, when testing how freely the floats were moving inside the bowl I found the side walls of the float bowl, while looking smooth, actually to be very rough - like a fine grit sandpaper. So polished that with a dremel and some very fine grit polishing compound. Now I have no proof that this actually did something, but every time I touched some part of the float assembly I felt those intermittent and sudden changes in performance got less and seem to be gone by now.

You might also want to consider resetting your float level, even if it seems to be correctly at 20mm. Hard to explain, but if you start playing with that you may find 20mm not being equal 20mm in SC terms.

While you are at it remove the MR nozzle/tube and have a look inside. The upper part (which sits in the venture) should be absolutely smooth inside - no scratches/imperfections.

Michael