Texas Two Step Taco

John Murray

Member
Cool. Dogs probably feel threatened by the bark of the big dog. I'd have thought it'd be only just barely getting into the powerband at 6300.. the rev range might go up a tad as you dial in the jetting and get more heat into the pipe. Timing should be very close.
 

Texasstar

Can't is a four letter dirty word
Cool. Dogs probably feel threatened by the bark of the big dog. I'd have thought it'd be only just barely getting into the powerband at 6300.. the rev range might go up a tad as you dial in the jetting and get more heat into the pipe. Timing should be very close.
Yes it was just on the pipe before it hit the rev limiter. The flat track guys are running 21 degrees. 2.5-2.7mm BTDC


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John Murray

Member
What CHT should we be looking to avoid?


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Ignore it, it's just another distraction. It'll get hotter than ideal but there's not much you can do about it apart from directing a good strong airflow over it while it's on the dyno. Listen for det (though it'll be hard with no silencer). On the dyno I run some 3" flex from the pipe through a truck muffler that quietens it down and takes the noise away somewhat. It's quiet enough that I can hear detonation with earmuffs on. With the air cooled motor in the Metralla on the street I used a fairly big silencer and even though it was still pretty loud any det was audible.
 

Texasstar

Can't is a four letter dirty word
It was glorious...road 1.5 miles blasting up through the gears until the shifter selector started hanging and I new exactly what it was. Pushed it home 1.5 miles. We need straight cut gears. Pushed the bearing out of the clutch hub again. My machinist neighbor said there is no way that transmission loctite would work with those forces. Time to stimulate Spain’s economy.
IMG_7654.jpg



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Texasstar

Can't is a four letter dirty word
Here is a video of the components showing the bearing thrust inward on the clutch housing for the bultaco Bandido Montadero


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Texasstar

Can't is a four letter dirty word
I used the M70 housing and bearing this time. Tonight I will press out the bearing and try the transmission loctite.


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John Murray

Member
There's a shallow recess around the bearing boss as well as in the back face of the hub. It looks like you may be able to fit a thin retainer plate that covers the outer race and attaches via screws to the basket. You might want to use some Loctite 620 as well. It's fixable.
 

Texasstar

Can't is a four letter dirty word
There's a shallow recess around the bearing boss as well as in the back face of the hub. It looks like you may be able to fit a thin retainer plate that covers the outer race and attaches via screws to the basket. You might want to use some Loctite 620 as well. It's fixable.
Now I get to tell Zeke he was right...well he wants to be a mechanical engineer. :)


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irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Why not machine a groove in the clutch hub and install a ring clip? With a ring clip, you could even run a thrust bearing.
 

Texasstar

Can't is a four letter dirty word
Why not machine a groove in the clutch hub and install a ring clip? With a ring clip, you could even run a thrust bearing.
We could do that but we would have to go to a thinner bearing or machine the rear housing for the clearance since the bearing currently sits flush with the housing. Another good option. Thank you.


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teazer

Well-Known Member
DTT BOTM WINNER
How about a different approach.

I am assuming that the bearing isn't moving. The basket is moving towards the crankcase.

Can you machine whatever is behind the clutch basket to fit a roller thrust washer to stop the basket (and gear) from moving inward. There is an existing flat surface fir the thrust bearing to ride against in the basket, so all it needs is enough space for the inner face and the bearing.

On older Suzukis there is a hardened washer either side of the equivalent to that bearing which is a long bronze bush. That is enough to stop things moving - most of the time because they act like thrust washers and contain/retain the basket laterally. When they changed to straight cut primary gears they kept those thrust washers.

A more involved solution could include a pair of back to back gears cut in different directions to eliminate side thrusts, but that would have to be the most complicated and expensive way to fix the issue.

It looks like AJR changed the clutch design when they came up with the straight cut primaries to include a roller bearing plus an inner thrust plate. It might be possible to use this part https://ajrmotocicletas.es/epages/c...950-45ce-8ec9-2ca023feb311/Products/AJ5000074 with slight modification.
 

Texasstar

Can't is a four letter dirty word
How about a different approach.

I am assuming that the bearing isn't moving. The basket is moving towards the crankcase.

Can you machine whatever is behind the clutch basket to fit a roller thrust washer to stop the basket (and gear) from moving inward. There is an existing flat surface fir the thrust bearing to ride against in the basket, so all it needs is enough space for the inner face and the bearing.

On older Suzukis there is a hardened washer either side of the equivalent to that bearing which is a long bronze bush. That is enough to stop things moving - most of the time because they act like thrust washers and contain/retain the basket laterally. When they changed to straight cut primary gears they kept those thrust washers.

A more involved solution could include a pair of back to back gears cut in different directions to eliminate side thrusts, but that would have to be the most complicated and expensive way to fix the issue.

It looks like AJR changed the clutch design when they came up with the straight cut primaries to include a roller bearing plus an inner thrust plate. It might be possible to use this part https://ajrmotocicletas.es/epages/c...950-45ce-8ec9-2ca023feb311/Products/AJ5000074 with slight modification.
Correct the bearing stays in place. The basket is moving. You and Ralf have the same approach. Ralf suggested a brass washer between the basket and the case. I would think it would need a roller since the basket is machining the gear for the shift selector. However the washer would be bathed in oil. BTW you are thinking like a German Mechanical Engineer!

So I noticed the key way in the straight cut gear kit we have been posting and realized that this kit is not for my Bultaco. It is for the 250cc motorcycles and is for the chain drives. https://ajrmotocicletas.es/Gear-primary-drive-and-clutc


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teazer

Well-Known Member
DTT BOTM WINNER
That must be because I'm a mechanical engineer and had an Austrian great grandfather..........

Ralph is obviously a very smart guy if he thinks the same way as me..... two very stable geniuses perhaps :D:D:D:D

OK, so back to our normally scheduled program. Look at a way to add a thrust washer and let's get this show on the road.
 

Texasstar

Can't is a four letter dirty word
This is the correct straight cut gears and modern clutch design from AJR
IMG_1201.jpg

for the Bultaco Bandido and Montadero
IMG_2214.jpg



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Texasstar

Can't is a four letter dirty word
That must be because I'm a mechanical engineer and had an Austrian great grandfather..........

Ralph is obviously a very smart guy if he thinks the same way as me..... two very stable geniuses perhaps :D:D:D:D

OK, so back to our normally scheduled program. Look at a way to add a thrust washer and let's get this show on the road.
I can’t wait to tell Zeke!


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John Murray

Member
There's very little side thrust on the bearing - the clutch is designed so that all of the spring force is self-contained within the hub, unlike the chain drive Bul clutch and most others. So it really won't take much to retain the bearing at all, a thrust washer behind the basket as Teazer suggested or a sheetmetal retainer ring over the top of the bearing would do it. If you really wanted to get quick-and-dirty (my favorite kind) you could just put a thin ring over the outer race and tack weld it down in 3 or 4 places. You'd have to grind the tacks off to change the bearing - not a big deal - but they last forever anyway.

Incidentally, and as someone who has battled primary drive issues for many years with big Buls, these sorts of problems commonly surface when the rotating mass is reduced and the rpm range raised, they're rarely a problem at all with the stock heavy flywheels. It's not the torque that causes the problems, it's the hammering from the intermittent impulses. So while a lighter rotating assembly certainly has its advantages it does make life difficult for everything downstream of the crank, even with the spring-and-cam drive pinion. Things get hammered and rattle loose.
 

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