Pete_Muller
Moderator
Fuel tank issue? Maybe a clogged vent?
2 cycle exhaust
- Thread starter Komet99
- Start date
rainman
Member
It starts good on the stand, and even on the ground. Vent not clogged. It just would bogged and died. I would understand if i had changed the gear ratio or clutch setup but i kept same weights from the other clutch, same carb setup too. Drove me crazy all day.
rainman
Member
That might be a reason, but didn´t even have time to warm up the engine. I am gonna try to change the clutch again.
Ted Hamilton
Helmet Painter / Racer
^^ Yet another reason to go direct-drive.... 
It keeps us fit for soccer season....or is that the other way around?
Back to pipes....has anyone tried a spring-actuated "slippy" that has baffles that open (or close) after a certain RPM/exhaust pressure is reached? Kinda' like a powervalve, but back in the pipe?
It keeps us fit for soccer season....or is that the other way around?Back to pipes....has anyone tried a spring-actuated "slippy" that has baffles that open (or close) after a certain RPM/exhaust pressure is reached? Kinda' like a powervalve, but back in the pipe?
Pete_Muller
Moderator
Not me. I did build a "double adjustable" pipe for my McCulloch enduro kart back in the mid-70's. (independent sliding of front and rear cones).
Huge potential, but the difficulty was mixture control through the range. It was extremely fast though.... for a while.
PM
Huge potential, but the difficulty was mixture control through the range. It was extremely fast though.... for a while.
PM
Ted Hamilton
Helmet Painter / Racer
@Pete_Muller -- As the saying goes, "they're always fastest right before they blow?" (or stick.)
Ted, on a one breath and turn left track it's pretty much not worth the trouble. Years ago we tried the carb trigger on the Yamaha kt on small dirt ovals and it worked ok just wasn't that great of a improvement now on the enduro circuit the trigger is a must have no matter what Rainman says lol later Chuck.
rainman
Member
Rainman says Justin Greene won our last race at Roebling Road without using the trigger on race 2 (Sunday), and he was slower with the trigger on Race 1 (Saturday). The trigger might be good if you are looking for the last 10ths or 100ths, but I don't think that is your case or mine, lol. At least not for now.
Rain, you're comparing apple's to oranges. All the top runners use the trigger. As far as Roebling Roads goes Saturday and Sunday were like night and day. Saturday you had a 25mph head wind not so much on Sunday. Buy the way that was a club race check out the national guys I bet 9 out of 10 use the trigger. As Mr. Pete Muller said on a earlier post " the walbro carb is a weed eater - chain saw carb at best, works best at idle or full throttle I 'll take his advice any day. I'm done later Chuck.
Pete_Muller
Moderator
IMO, the key to getting a trigger to work well is to set it up so the engine is as rich as it can possibly be at clutch slip speed (somewhere near peak torque, or between peak torque and peak horsepower). Most people have experienced the ability to essentially open the high speed jet a bunch at clutch slip speed... the engine will almost take all the fuel you can pour to it right there in that spot of the power band (and this "effect" can be greater or less depending on the shape of the exhaust pipe).
Why the above is important is, the goal is to keep the EGT under control down in the "meat" of the power band range, so that when you pull the trigger (and it's set up properly), the engine goes fairly lean (but not TOO lean) in the over-rev portion of the power band (i.e. beyond peak horsepower).
What that buys is an increase in EGT, and since the speed of sound increases with temperature, the exhaust pipe acts like it's been shortened (which is exactly what's needed for over-rev).
It's a bit of a balancing act to get the pipe length correct AND mixture correct for both of those scenarios (clutch slip and pulling hard just after the clutch has engaged.... vs. over-rev at the top end).
While the trigger IS there for leaning out the engine (and richening it up when you let get of it), the primary advantage of that comes from what it does to the EGT -- which changes the speed of sound and consequently how it the exhaust pipe "acts".
PM
Why the above is important is, the goal is to keep the EGT under control down in the "meat" of the power band range, so that when you pull the trigger (and it's set up properly), the engine goes fairly lean (but not TOO lean) in the over-rev portion of the power band (i.e. beyond peak horsepower).
What that buys is an increase in EGT, and since the speed of sound increases with temperature, the exhaust pipe acts like it's been shortened (which is exactly what's needed for over-rev).
It's a bit of a balancing act to get the pipe length correct AND mixture correct for both of those scenarios (clutch slip and pulling hard just after the clutch has engaged.... vs. over-rev at the top end).
While the trigger IS there for leaning out the engine (and richening it up when you let get of it), the primary advantage of that comes from what it does to the EGT -- which changes the speed of sound and consequently how it the exhaust pipe "acts".
PM
rainman
Member
I understand that and don't disagree, there is no way I am gonna disagree with Pete, what I mean is that if you are not so fast or so good paying attention to one more thing like using the trigger will probably make you slower instead of helping. That's probably why Justin was faster without the trigger. Way faster, not just because of the wind. Ask him. you had already left when he raced and talked about that himself. If you are really good you might not even need a trigger, like most people used to do in ICA changing the carb setup through different areas of the track. That's what I have tried at some races when you told me not to touch it, but in fact what I did is exactly what the trigger does. Problem is it is way harder to do that on a laydown. By the way my Sudam started fine on Wednesday. Still wondering what the real problem was.
Pete_Muller
Moderator
rainman
Member
To be honest I do not have the knowledge to disagree with you.@rainman,
Please don't hesitate to disagree! It's that type of exchange that can cause us (or in this case "me") to re-evaluate what we think we know.
Ideally, everyone wins in that type of an exchange of ideas or thoughts or even speculation.
PM
Pete_Muller
Moderator
Rainman,
Everyone that participates in this Forum has knowledge... could have been obtained anywhere from "the school of hard knocks" to a Masters degree in Engineering, but every bit of it has value.
Everyone that participates in this Forum has knowledge... could have been obtained anywhere from "the school of hard knocks" to a Masters degree in Engineering, but every bit of it has value.
rainman
Member
Direct Drive won't make it on dirt ovals, Ted. It's all about momentum.^^ Yet another reason to go direct-drive....
Back to pipes....has anyone tried a spring-actuated "slippy" that has baffles that open (or close) after a certain RPM/exhaust pressure is reached? Kinda' like a powervalve, but back in the pipe?
rainman
Member
Sure I have leaned something in over 25 years racing and working on karts, but I do not have a formal mechanical knowledge. Just listen to people like you.