TM36 and Acerbis tank
#31
09-16-2012, 02:37 AM
Join Date: Sep 2009
Location: Abilene, TX
Posts: 5,050
After the excellent results I got on my first outing on that 94 degree day, I decided to take another ride yesterday while it was 60 degrees. Yep...it's Texas. It's 94 one day and 60 the next...LOL!
So, I fire it up on the choke, and it starts superbly. It takes longer to get off the choke at this point for a smooth idle. I start rolling away, and the bike definitely has a rough spot until I can tell I'm getting the extra fuel from the pumper circuit. It gets better as the bike warms up, but it's definitely not as smooth as it was on the 94 degree day. At a very small throttle opening it's yielding all the symptoms of being a bit lean. Once you start opening the throttle any to get the benefit of the pump or you're on the needle/needle jet and main portion of the throttle, things are great.
I've made a somewhat lean assessment at this point, but there is an excellent 5 page tuning manual for this carb, and it gives many good pointers for different scenarios. Without going into boring detail on the manual, it basically boils down to two elements of the pilot circuit. The manual gives some very excellent detail on how these two elements interact. While our carb has a pilot jet, the TM36 has a pilot jet and pilot air jet. That sounds complicated, but the manual gives some really understandable info about how they work in concert. I am using the richest pilot jet I have on hand, a 17.5. But the manual's description of my scenario sounds identical to the pilot air jet being the better item to try next. To richen up the part of the throttle I need, I go to a smaller pilot air jet to richen it. Yes, smaller, because the smaller air jet causes a stronger vacuum signal at the pilot jet. Interesting deal that sounds backward at first glance. Anyway, the carb comes with a 1.0 pilot air jet, and I installed a 0.9 air jet. Doesn't sound like much, but the manual says it equals 1 full change on the pilot jet. The pilot air jet, however, has more influence from about 1/8 to 1/4th throttle before transitioning to the needle, while the pilot jet has more influence from idle to 1/8th throttle.
So today I go for a ride in 63 degree weather for an almost identical comparison. The bike warms quickly after the choke is off, and even while the engine is still a bit cool, it accelerates away way smoother with a very small throttle opening. I try to accelerate slowly to keep the influence of the pump to a minimum. It's way different from yesterday. After the bike warms up even more, the throttle response seems spot on at all rpm and throttle positions. The cooler conditions revealed that my initial setup was a bit too lean just off idle apparently, and slightly richening up that small throttle opening position was what was needed. This carb is actually almost fun to work on, and Mikuni provides some really excellent material in their manual that doesn't require an engineering degree to understand.
So, I fire it up on the choke, and it starts superbly. It takes longer to get off the choke at this point for a smooth idle. I start rolling away, and the bike definitely has a rough spot until I can tell I'm getting the extra fuel from the pumper circuit. It gets better as the bike warms up, but it's definitely not as smooth as it was on the 94 degree day. At a very small throttle opening it's yielding all the symptoms of being a bit lean. Once you start opening the throttle any to get the benefit of the pump or you're on the needle/needle jet and main portion of the throttle, things are great.
I've made a somewhat lean assessment at this point, but there is an excellent 5 page tuning manual for this carb, and it gives many good pointers for different scenarios. Without going into boring detail on the manual, it basically boils down to two elements of the pilot circuit. The manual gives some very excellent detail on how these two elements interact. While our carb has a pilot jet, the TM36 has a pilot jet and pilot air jet. That sounds complicated, but the manual gives some really understandable info about how they work in concert. I am using the richest pilot jet I have on hand, a 17.5. But the manual's description of my scenario sounds identical to the pilot air jet being the better item to try next. To richen up the part of the throttle I need, I go to a smaller pilot air jet to richen it. Yes, smaller, because the smaller air jet causes a stronger vacuum signal at the pilot jet. Interesting deal that sounds backward at first glance. Anyway, the carb comes with a 1.0 pilot air jet, and I installed a 0.9 air jet. Doesn't sound like much, but the manual says it equals 1 full change on the pilot jet. The pilot air jet, however, has more influence from about 1/8 to 1/4th throttle before transitioning to the needle, while the pilot jet has more influence from idle to 1/8th throttle.
So today I go for a ride in 63 degree weather for an almost identical comparison. The bike warms quickly after the choke is off, and even while the engine is still a bit cool, it accelerates away way smoother with a very small throttle opening. I try to accelerate slowly to keep the influence of the pump to a minimum. It's way different from yesterday. After the bike warms up even more, the throttle response seems spot on at all rpm and throttle positions. The cooler conditions revealed that my initial setup was a bit too lean just off idle apparently, and slightly richening up that small throttle opening position was what was needed. This carb is actually almost fun to work on, and Mikuni provides some really excellent material in their manual that doesn't require an engineering degree to understand.
I need one
#33
09-22-2012, 07:58 PM
Join Date: Sep 2009
Location: Abilene, TX
Posts: 5,050
I'm typing this while out at our riding area south of town...camping and riding for 3 days. This is the first chance I've had to do some actual singletrack, and it's some gnarly singletrack. It's been a little warm at right around 90 for the day's high, and the carb has been working perfectly. No bogging, ho hiccups, no blubbering, so the jetting must be just about perfect. I've ridden yesterday and today for a total of about 70 miles and will ride again tomorrow.
I'm finding that I don't have to fan the clutch hardly at all even lugging it in any gears. It pulls amazingly cleanly. I thought that would be the area where maybe the CV carb would have an advantage, but this thing tractors up anything even when you're a bit low in the rpm band. I'm just not finding anything to carp about at this point and everything to rave about. I got into trouble a couple of times in spots where I was normally still on the gas with the stock carb, but almost didn't realize how fast the bike had accelerated to with this carb. Lofting the front wheel is now a piece of cake, easy to do at will. It's really helped a couple of times as there has been a couple of big rains that really make some holes and wheel eating ruts. It was nice being able to pick the front wheel up when surprised by a washout hidden by weeds or a huge bike stopping cross rut. I am stoked.
I'm finding that I don't have to fan the clutch hardly at all even lugging it in any gears. It pulls amazingly cleanly. I thought that would be the area where maybe the CV carb would have an advantage, but this thing tractors up anything even when you're a bit low in the rpm band. I'm just not finding anything to carp about at this point and everything to rave about. I got into trouble a couple of times in spots where I was normally still on the gas with the stock carb, but almost didn't realize how fast the bike had accelerated to with this carb. Lofting the front wheel is now a piece of cake, easy to do at will. It's really helped a couple of times as there has been a couple of big rains that really make some holes and wheel eating ruts. It was nice being able to pick the front wheel up when surprised by a washout hidden by weeds or a huge bike stopping cross rut. I am stoked.
#35
09-23-2012, 10:03 PM
Join Date: Sep 2009
Location: Abilene, TX
Posts: 5,050
Got back from the 3 day riding stint out at the club's riding area. Got to ride with a bunch of the other club members. They get a kick out of me having the only street legal type bike out there. It's funny riding around with KTM's, CRF Honda's, KX's and such. I always come back from these weekends with almost no pics. If I'm doing a ride alone, it will be just scenery pics, and if I'm riding with some of the other guys, we don't stop for picture taking sessions. But I did at least take a couple. The one with the 60 mile sign is where you're about 2/3 completed in our annual state enduro. Overall there's about 100 miles of singletrack out there, and a good bit of it is downright gnarly. The recent heavy rains really left a lot of exposed rocks and roots. Some of the climbs were really loose and challenging.
On the TM36, without question this carb pretty much changes the nature of the bike. It will allow you to lug the bike but still be able to accelerate out of the lug with total smoothness and crisp response. That part still amazes me. Acceleration to redline happens fast. I've already gone on and on about the carb, so I'll just close. I did not detect any rough edges in the jetting, so I'm pretty well tuned in. On fuel mileage, since I didn't fill up at a pump while out there, I did check mileage and the amout I used from my graduated motorcycle fuel can from one ride. With 45 miles on the clock...true mileage with a calibrated Vapor unit...I couldn't get it to take a full gallon...and probably 90% of that all challenging singletrack. It appears that it won't be a gas hog at least. I noticed the same thing with durielk's pumper carb equipped KLX on our Colorado rides.
If I sound like a salesman for Mikuni, I guess you could say so. I see now why so many have installed this carb on KLX300's and the "S" and "SF" models. I'd love to have my 3 years back when I was running the OEM CV carb.
On the TM36, without question this carb pretty much changes the nature of the bike. It will allow you to lug the bike but still be able to accelerate out of the lug with total smoothness and crisp response. That part still amazes me. Acceleration to redline happens fast. I've already gone on and on about the carb, so I'll just close. I did not detect any rough edges in the jetting, so I'm pretty well tuned in. On fuel mileage, since I didn't fill up at a pump while out there, I did check mileage and the amout I used from my graduated motorcycle fuel can from one ride. With 45 miles on the clock...true mileage with a calibrated Vapor unit...I couldn't get it to take a full gallon...and probably 90% of that all challenging singletrack. It appears that it won't be a gas hog at least. I noticed the same thing with durielk's pumper carb equipped KLX on our Colorado rides.
If I sound like a salesman for Mikuni, I guess you could say so. I see now why so many have installed this carb on KLX300's and the "S" and "SF" models. I'd love to have my 3 years back when I was running the OEM CV carb.
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