Any new ideas for softer thumb throttle?

[YFZRob]

Hey guys. I suffer from severe arm pump when racing my 88 in hare scrambles. I tried switching to a twist, but can't stand it....I need a thumb throttle back. I have gone through my throttle assembly and made 100% certain all parts are operating smoothly and as easily as possible. I have lubed the crap out of the cable and it's still too stiff. I did some searching and noticed the 400EX throttle works with some modifications. Would this be the best set up to try? Anyone consider the Terry Cable EZ pull throttle? I know JL ATV has an adjustable lever, but I don't think that'll cure my arm pump issues. I'm tired of losing positions in a race because my thumb is paralyzed!

Thanks!
Rob

[knobbyboy]

I use the thumb lever from a TRX90. Its longer and it will bolt up to the 250R or 400EX unit.

[250Renvy]

I've never used it, but I saw some video of Chris Earlywine highly recommending it when he was alive.

Boyesen shokout

http://www.boyesen.com/cwo/ATV/Products#shokout

[YFZRob]

Originally posted by knobbyboy
I use the thumb lever from a TRX90. Its longer and it will bolt up to the 250R or 400EX unit.

Any year on the TRX90 lever?

[YFZRob]

Originally posted by 250Renvy
I've never used it, but I saw some video of Chris Earlywine highly recommending it when he was alive.

Boyesen shokout

http://www.boyesen.com/cwo/ATV/Products#shokout

Yeah, I've thought about that too....

[knobbyboy]

I think any year but mine came off a 98 trx90 and bolted right up to my stock 250R. A friend did the same thing with the 400ex.

[matt250r21]

What carb are you running? On my 38 PWK's the throttle was stiff as hell. I cut a few coils off the spring inside the carb that is on top of the slide and there was a night and day difference. Now it is easy to work and has never given me any problems. I tried a 400EX thumb throttle once but could never get it to open the slide all the way on the 38 PWK no matter what I did to it.

[YFZRob]

Originally posted by matt250r21
What carb are you running? On my 38 PWK's the throttle was stiff as hell. I cut a few coils off the spring inside the carb that is on top of the slide and there was a night and day difference. Now it is easy to work and has never given me any problems. I tried a 400EX thumb throttle once but could never get it to open the slide all the way on the 38 PWK no matter what I did to it.

Yes, 38 PWK A/S here too. Traditionally, cutting coils will stiffen a spring, but maybe that's not the case in this situation. Maybe between a couple coils and the TRX90 thumb throttle, it'll be manageable. A few powersellers on ebay have brand new 400ex throttle assemblies for under $50 shipped. I may still give the 400ex assembly a shot and see if I can get a motion pro cable with an adjustment section in the middle of the cable for more adjustability once I modify the throttle stop. I'll figure out something....got until December 6 for my next race. Thanks guys!

[86 Quad R]

Originally posted by matt250r21
What carb are you running? On my 38 PWK's the throttle was stiff as hell. I cut a few coils off the spring inside the carb that is on top of the slide and there was a night and day difference. Now it is easy to work and has never given me any problems. I tried a 400EX thumb throttle once but could never get it to open the slide all the way on the 38 PWK no matter what I did to it.

this is what i do. along with a new throttle cable it makes it really easy on the thumb.

[YFZRob]

Okay, I made a decision...

Ordered up a TRX90 lever, new cable (even though the one I am using now has maybe 30 hours on it, but 4 years old), and new honda guts for the housing (seal, bushings, cam assembly, cotter pin, and washers). I'll see how that is and go from there with the slide spring.

[atvmxr]

dont forget about the slide and carb housing... my throttle was getting stiff and it was because the coating on the slide was coming off and galling up the movement of it...

[YFZRob]

That won't be an issue here....same age on the 38 PWK...about 30 hours on it. thanks for all the suggestions guys!

[matt250r21]

There is also a small return spring inside the 250R thumb throttle housing that I leave out. Every little bit helps.

[YFZRob]

Originally posted by matt250r21
There is also a small return spring inside the 250R thumb throttle housing that I leave out. Every little bit helps.

Yeah, forgot to mention that....it's getting pulled too. I'll try everything first without cutting the slide spring. If it still feels too stiff, I'll cut the spring. I've gotta work this thing for nearly 2 hours, so it has to be easy. I can easily race my Prairie without arm pump, so it's definitely just an issue of getting it softer/lighter. 2 races ago I lost the lead because of arm pump and the last race I won with a twist, but barely....I know I would have been faster with a thumb, especially as the course got torn up.

[YFZRob]

Okay, problem solved and solved well! I got the new OEM guts, including new bushings inside the housing with a TRX90 thumb section and a new MP cable. I also cut about 1.5 coils off the PWK slide spring and removed the return spring in the throttle housing. The difference....HUGE!! It's probably about 10% stiffer than a 400ex or z400! Before it was easily 50% stiffer. It's now softer than my Prairie 700 which I can race for 2 hours without arm-pump, so I should be set up just right for my next hare scramble.

Anyway, thanks again for the support guys!!

[trx310R#24]

ride more. that will fix it thats what i did...

[wilkin250r]

What carb are you running?

I could take another look at it, but I could swear my throttle is 10% lighter than a 400EX, and I've never cut any coils off my slide spring, and I still have the return spring in my throttle housing.

[YFZRob]

38 PWK A/S. Maybe it is lighter than a 400EX...just from my previous experience years ago with them, it still feels a tad stiffer, but WAYYY better than stock, even with a decent cable. The TRX90 lever made a big difference, the only problem is spacing the housing farther away from the grip to put it in the correct position, which pushes the front brake lever a tad far inward for my liking. Either way, I shouldn't have any arm pump issues now.

[FL-R]

I pulled the throttle return spring out, Greased up some of the parts in the thumb throttle a cliped a few coils on the spring in the carb and it made a big diff, Next im going to put a new cable in and trx 90 lever. Thanks for the ideas

[Hughes#34]

all you have to do is take the small return spring out of the thumb throttle housing which takes less than 5 mins, if you dont know how to do that, take the top cover off and there is like a 10m nut remove that and lift the half moon shape piece and there is a small spring under there that is really not needed take it out and put back together. And you really dont need to cut the spring down in the carb slide. I wasn't sure at first either but I took it to Mark at Baldwin Motorsports and all he did was stretch the spring out and put it back together that way you dont get any play and it makes a huge difference

[Hughes#34]

if you want to make your clutch a lot easier too, you can take the arm where the cable connects on the motor and bend it staight. you may have to make a small grind on the edge of you cylinder if the arm rubs depending what jug your running. But you will see a big difference there too.

[YFZRob]

Originally posted by Hughes#34
if you want to make your clutch a lot easier too, you can take the arm where the cable connects on the motor and bend it staight. you may have to make a small grind on the edge of you cylinder if the arm rubs depending what jug your running. But you will see a big difference there too.

Great idea too! Thanks for the input!

[JTRtrx250r]

besides everything already mentioned....you can alway's take the spring to the grinder and "thin" out the coils, just a tad off the outside of the spring makes a HUGE diffrence and the cheapest/easiest thing I do to all my stiff carb springs

you can always take it off but cant put it back, so go slowly till if feels about what your after. an old junker carb spring is always good practice