Texas Two Step Taco

John Murray

Been Around the Block
This is what I practiced that first couple of times, pull to the line, load the clutch, half throttle off the line to see what it would do. Smiled because the rotor had enough momentum to turn the big tire.


Now to put it on the rev limiter and do the same thing but be on the pipe and stay there. It’s all clutch and not letting go of that last 10% too quickly. Repetition.


Sent from my iPhone using Tapatalk
I might be wrong about this - and Teazer would have a much better idea than me so I'd love to read his comments - but this start line plan seems to lack commitment. I'd be more inclined to ditch the limiter and use lots of revs to jerk it off the line quickly, and in one motion. If you're gonna finesse the clutch the race is already lost. It'll take some practice to get comfortable with it but it's the most critical part of the run. And if it won't let you release the clutch in one smooth motion with lots of revs - and I think it will - then maybe you should reduce the tire width until it will. Your thoughts Teazer?
 

Texasstar

Can't is a four letter dirty word
I might be wrong about this - and Teazer would have a much better idea than me so I'd love to read his comments - but this start line plan seems to lack commitment. I'd be more inclined to ditch the limiter and use lots of revs to jerk it off the line quickly, and in one motion. If you're gonna finesse the clutch the race is already lost. It'll take some practice to get comfortable with it but it's the most critical part of the run. And if it won't let you release the clutch in one smooth motion with lots of revs - and I think it will - then maybe you should reduce the tire width until it will. Your thoughts Teazer?
Those were Ricky Gadsens words about the last 10% and he was running a 200 plus whp stock swing arm bike. With 42whp I don’t think we will have that problem. He said the biggest problem is not loading the clutch before launching. With his current stock bike he has been running in the 9’s.

With the Taco and wheelie bars I think we can hook and make a smooth release.


Sent from my iPhone using Tapatalk
 

teazer

Over 1,000 Posts
DTT BOTM WINNER
Forget about what Ricky G has to say. What I mean by that is that he has skills that you and I could only dream about and on top of that he is riding a 150-200hp bike and his skill is needed. With even stock big HP bikes, they make so much power that they can flip, so the rider must get just enough power to the ground and not much more.

With a lot less HP, we need thoretically need to come off the line at peak torque revs and never drop much below that. On a two stroke, peak torque is not much lower than peak HP revs, so we use a lot of revs. Yes we want to be smooth, but that doesn't mean slow. It means getting the clutch all teh way out and throttle wide open within a fraction of a second.

The value of a rev limiter is that the throttle can already be wide open before leaving the line, but it's another tool to learn how to use. I tried that on the Phat Trakka and for whatever reason, I never got to grips with it. I also had a situation with large first to second gap, so I had to overrev in first to stay in the powerband when it slotted into second, so my shift point was different in first than the other gears. That can all be managed with modern electronics which helps top riders to keep breaking records, but we are at the stone age end of that evolution and have to pick and choose which tools we want to learn how to use.

With simple bikes, I think the best approach is KISS and change one thing at a time. I would suggest that you get it running cleanly on the dyno and then do a lot of practice runs at the strip. When you are knee deep in records and totally consistent, that's the time to look at the toys.

I helped a friend build a drag race bike in the STOCK class and he is even slower than I am, so we have been going to the strip and doing lots of runs. I am the analog data logger. Time slips confirm things but listen to how the engine sounds in each gear. Then he gets feedback and encouragement and tries again until he gets it right. Then we changed jets and timing but it was really about practice, and by the time we left, he had cut half a second off his previous best 1/4 mile run.

In his case it would be nice to log revs and throttle position to show him what he's doing, but only until he is giving it everything it's got.

Keep going to the strip and keep the revs up - all the time. The more you practice, the more you are able to slow down things in your brain. For me, the first run of a weekend, always seems really freaky fast which it of course isn't and by the end of the weekend, the bike feels slower because I am more able to go faster as I start to process things faster.

Practice, practice, practice and take a spotter if possible who can tell you what is going on.
 

Texasstar

Can't is a four letter dirty word
Forget about what Ricky G has to say. What I mean by that is that he has skills that you and I could only dream about and on top of that he is riding a 150-200hp bike and his skill is needed. With even stock big HP bikes, they make so much power that they can flip, so the rider must get just enough power to the ground and not much more.

With a lot less HP, we need thoretically need to come off the line at peak torque revs and never drop much below that. On a two stroke, peak torque is not much lower than peak HP revs, so we use a lot of revs. Yes we want to be smooth, but that doesn't mean slow. It means getting the clutch all teh way out and throttle wide open within a fraction of a second.

The value of a rev limiter is that the throttle can already be wide open before leaving the line, but it's another tool to learn how to use. I tried that on the Phat Trakka and for whatever reason, I never got to grips with it. I also had a situation with large first to second gap, so I had to overrev in first to stay in the powerband when it slotted into second, so my shift point was different in first than the other gears. That can all be managed with modern electronics which helps top riders to keep breaking records, but we are at the stone age end of that evolution and have to pick and choose which tools we want to learn how to use.

With simple bikes, I think the best approach is KISS and change one thing at a time. I would suggest that you get it running cleanly on the dyno and then do a lot of practice runs at the strip. When you are knee deep in records and totally consistent, that's the time to look at the toys.

I helped a friend build a drag race bike in the STOCK class and he is even slower than I am, so we have been going to the strip and doing lots of runs. I am the analog data logger. Time slips confirm things but listen to how the engine sounds in each gear. Then he gets feedback and encouragement and tries again until he gets it right. Then we changed jets and timing but it was really about practice, and by the time we left, he had cut half a second off his previous best 1/4 mile run.

In his case it would be nice to log revs and throttle position to show him what he's doing, but only until he is giving it everything it's got.

Keep going to the strip and keep the revs up - all the time. The more you practice, the more you are able to slow down things in your brain. For me, the first run of a weekend, always seems really freaky fast which it of course isn't and by the end of the weekend, the bike feels slower because I am more able to go faster as I start to process things faster.

Practice, practice, practice and take a spotter if possible who can tell you what is going on.
Thank you Teazer. Bull by the horns and hold on for 8 seconds. ;)


Sent from my iPhone using Tapatalk
 

Texasstar

Can't is a four letter dirty word
Checked the tach and it was set wrong.
Sent from my iPhone using Tapatalk
 
Last edited:

Texasstar

Can't is a four letter dirty word
Problem solved I had the tach set at 2 sparks per revolution

Here is the shift light set at 7500 rpms




Sent from my iPhone using Tapatalk
 
Last edited:

Texasstar

Can't is a four letter dirty word
IMG_1343.jpg

175 lbs 360cc honda single 90whp ran 6.5 in the 1/8 on methanol.


Sent from my iPhone using Tapatalk
 

Texasstar

Can't is a four letter dirty word
The track was packed so we were only able to make 3 runs last night. The first two runs I red lighted like a virgin on a first date. Bb said you do realize you are not suppose to leave on the second stage light. Lol I had premature evacuation. Both of those runs are on the video.

The third run .50 reaction time but I didn’t want to red light again. I rolled off the throttle and kept it at the shift light which is set at 7500 rpms and it didn’t die/ nosedive this time but only ran a 9.5 in the 1/8. Checking the needle. May have a fuel flow issue. Good news is the clutch held up.


Sent from my iPhone using Tapatalk
 

John Murray

Been Around the Block
I think we were running out of gas. What do y’all think?


Sent from my iPhone using Tapatalk
I hope I'm not leading you on a wild goose chase here; keep in mind this is just a possibility, not a definite diagnosis.

I've had similar behaviour with a couple of reed valve engines. Typically the symptoms include the following:

The initial startup after a rebuild takes a little longer than usual

It needs enrichment to start, but then after a very brief warmup the low speed circuit can be leaned out substantially, a little more than usual.

After the brief warmup and leanout, response is good, it sounds good and shows no signs of being rich or lean

On acceleration under load (either on track or dyno) the initial response is good but after a couple of seconds the power fades or just cuts out altogether, and only returns after a couple of seconds with gobs of throttle.

At the end of a full throttle run, the engine appears to cut out again while decelerating on the closed throttle, it may fail to respond while blipping for a downshift.

On a dyno run - and this won't show up on an inertia dyno - the torque may drop off after the first few seconds and level out.

It took me a long time to work out what was happening, and this is my interpretation. At idle and low speed/loads, the reed valves barely open at all, especially if the reed is big in relation to the engine. Without a load the fuel separates out onto the reed and just drools into the engine. Because of this you have to enrich it quite a bit to fire it up, most of the fuel is just running down into the crankcase.

After a brief period of this the fuel puddle in the crankcase builds up to the point the crank starts to throw it around and the engine suddenly goes rich so you lean it off until everything sounds good.

This is all well and good but when you open the throttle and apply a load the puddle is stirred up by the airflow and this temporary reservoir of added fuel confuses the jetting process. If you use an inertia dyno that only loads the engine briefly you end up with very lean jetting. On the track it'll probably leave the line fine but once the puddle is dried up it runs very lean. It might recover a little with a handful of throttle or as the engine warms a little.

On deceleration you may find the engine again doesn't want to run until the puddle in the crankcase has re-formed, but by the time you get back to the pits it will be idling perfectly.

What's the workaround for this? More jet mainly, and avoiding over-long periods of idling and warmups. I'm not a fan of inertia dynos, you can't jet properly with them because the loaded duration is too brief and you will usually end up lean.

Anyway, it's just a possibility - in your video you seem to have sufficient fuel off the line but then go super lean so it's worth considering. But I can't say with any certainty that it's the cause.
 

Texasstar

Can't is a four letter dirty word
It would be so much easier just to have you at the track. That sounds about how each run ended up going.

So it starts fine idles fine. It did a nose dive on the first two runs in the same place. It wasn’t the flywheel because as soon as it got fuel it was back on the pipe. When I rolled on hard on the throttle up to the rev limiter it did the same thing last the shift light. When I pulled up to get the time ticket it died. Pushed it all the way back.

Now on the third run I camped out on the line had a cappuccino and then launched. Kept it at the shift light which was 7500 and kept it lit down the track. Pulled up to get my time ticket this time the one that actually had a time and it died.

Did I read the plugs like I should have? Nope.

I will pull the jets out to the track and do some more testing and tuning this time instead of doing testing and wtf’kng.


Sent from my iPhone using Tapatalk
 

teazer

Over 1,000 Posts
DTT BOTM WINNER
I love Bill's reaction.

Those runs were almost as bad as my last time at the strip where first off the kill microswitch stuck "closed" for almost a second and finally stuck closed so I also had that walk of shame. Followed by a series of equally horrible runs where components did not do as they were supposed to. That's why we do shakedown runs and we go when there's no one that knows us....

Your bike dies off the line as soon as the clutch is fully out and the load is too high. Looks like the clutch is engaging too fast and I suspect that the throttle isn't wide open at that point. Set up a simple TPS. all you need is a microswitch that is linked to the throttle or a second cable on the throttle (twin pull or splitter) so that at full throttle it makes a connection. That can be connected to a small battery and LED rear lamp so your team captain can watch and he gets to hit you with a long stick fr every time he sees it go out. It's analog and very basic, so feel to upgrade any part of that to actually log results.

The thing bogs pretty soon, and the revs should not drop like that. It could be loading up with unburned fuel or it could be that the clutch is out too far too soon.

John's observations about large reed cages make sense, but your motor should come off the line at 7000 or more and not drop until it goes into second gear so we should be at peak load off the line. My guess is too rich combined with too much clutch release too soon. I went back and watched the "clean out" video and it has a similar stutter but came off the line much cleaner in that earlier run. I don't like holding a motor at the red line for seconds at a time on the line and a launch rev limiter tends to cause excess fuel to build up in the cases which John mentioned.

Get the launch right first and then look at the other symptoms one at a time. MPS sells a pneumatic clucth lever that is easy to adjust and consistent. It's not cheap but may resolve one issue.
 

Texasstar

Can't is a four letter dirty word
I love Bill's reaction.

Those runs were almost as bad as my last time at the strip where first off the kill microswitch stuck "closed" for almost a second and finally stuck closed so I also had that walk of shame. Followed by a series of equally horrible runs where components did not do as they were supposed to. That's why we do shakedown runs and we go when there's no one that knows us....

Your bike dies off the line as soon as the clutch is fully out and the load is too high. Looks like the clutch is engaging too fast and I suspect that the throttle isn't wide open at that point. Set up a simple TPS. all you need is a microswitch that is linked to the throttle or a second cable on the throttle (twin pull or splitter) so that at full throttle it makes a connection. That can be connected to a small battery and LED rear lamp so your team captain can watch and he gets to hit you with a long stick fr every time he sees it go out. It's analog and very basic, so feel to upgrade any part of that to actually log results.

The thing bogs pretty soon, and the revs should not drop like that. It could be loading up with unburned fuel or it could be that the clutch is out too far too soon.

John's observations about large reed cages make sense, but your motor should come off the line at 7000 or more and not drop until it goes into second gear so we should be at peak load off the line. My guess is too rich combined with too much clutch release too soon. I went back and watched the "clean out" video and it has a similar stutter but came off the line much cleaner in that earlier run. I don't like holding a motor at the red line for seconds at a time on the line and a launch rev limiter tends to cause excess fuel to build up in the cases which John mentioned.

Get the launch right first and then look at the other symptoms one at a time. MPS sells a pneumatic clucth lever that is easy to adjust and consistent. It's not cheap but may resolve one issue.
Humiliation isn’t a problem. I have been married for 30 years. Lol. It also explains my 2 second 60’ time on my third run when it didn’t bog. So the first thing I will do is do what y’all said to do in the first place and go to a smaller rear tire. I zoomed in on my first two runs and can see what you are saying Teazer. It’s all about the clutch.


Sent from my iPhone using Tapatalk
 

DTT Bike Of The Month Gallery

DTT Light or Dark

www.jadusmotorcycleparts.com
shop.themotoworks.com
www.cognitomoto.com
https://www.townmoto.com
www.speedmotoco.com
www.lostapostle.ca/
www.sparckmoto.com
Top Bottom