Question for the experts…Modifying the Shift Star

[bscottr]

Here’s the background:

In another post (link below), I posed the question of shift problems with my ’01 KX250. Basically, the problem is that I hit neutral very often when shifting up and down between first and second. Shifts between other gears are fine (no false neutrals). In the thread we covered several things such as shifting techniques, shifter placement and polishing the internals. I believe my shifting technique is fine, however, I tried different placements of the shifter with no luck.

http://www.dirtrider.net/forums3/showthread.php?threadid=31550&goto=newpost

As a result of the thread I polished the internals (shift drum/forks, shift shaft/selectors and the shift star or drum plate). I haven’t had an opportunity to try the results yet as Eric has my top end and is fixing me up with a 265 kit. :confused: :cool: While polishing, I made an observation that brings me to my question. If you have Eric’s book, page 197 has a great photo.

On my bike I noticed that on the shift star, the “points” of the star that cradle the gear set lever (the rolling follower with spring) in neutral appear quite a bit higher than those points on the remainder of the star. I assume this is to make finding neutral easier when intended. However, I believe this may also contribute to my problem of finding neutral when not intended.

Once I reassembled the bottom end, I carefully watched the shift star and follower while shifting through the gears. Although smoother as a result of polishing, shifting is still difficult between 1st and 2nd in either direction. Because of the height of the neutral points, the follower spring tension is very difficult to overcome. I noticed in the picture in Eric’s book that the neutral points do not appear higher than the other points. I have yet to put a micrometer on my shift star to measure the height difference and in looking at the photo can only judge the points appear equal. Here are the questions:

Should the points be equal? What disadvantage would there be in making the points equal in height to the others and yet maintain their basic shape? Has anyone tried this mod?

Changing the return spring is also an option. Has anyone tried this with success? If so, which spring?

98-99 Part number 92145-1063
’00 Part number 92145-1315
’01 Part number 92145-1383

I appreciate the help.

Scott

 

[A.J]

I wonder how much a new shift star is from Kawasaki? You may be on to something on the grinding of the neutral position to help it shift past it on the 1st to 2nd shift. Might be not be a very costly experiment to try when you get it back together, if it doesn't work just buy a new one.
As for the detent spring, I guess you could try a lighter one but it may also help it kick out in some of the other gears if the dogs are worn. The springs are really inexpensive for sure - I don't now about the shift star though.

 

[bigred455]

Scott very good observation,i have a 00 kx 250 since new.I have the same problem from 1st to 2nd or 2nd to 1st,it seems like their is a big gap from 1st to 2nd it likes to catch neutral.I get smooth shift's with the power on from 2nd on up regardless what the mag's say.I had my bottom end apart to replace the big end rod bearing,my friend is a team kawasaki mechanic for the drag bikes. we had the cases apart and he was showing me when you turn the shift drum and watching the shift star how smooth all the other gears were from 2nd on up ,but from 1st to 2nd or 2nd to 1st it seemed like their was too much tension.He put a softer detent spring in, i have had it in since, the 1st to 2nd is not any better.I just got off the phone with my friend he said if you take some of the shift star off where it would sit in neutral,IT would jump into neutral from 1st or 2nd on it's own.Bad idea, actually it is a good idea i think,but he said it would not work it will jump into neutral on it's own.I have just lived with the 1st to 2nd not that we are in that gear that much,but i shift very aggressive from first to 2nd in tight spots.

 

[azcourt]

Here is a thread in a YZF forum. It is describing the shift star mod on a YZ250F, but I think the same thing should work on the KX. click here

 

[bscottr]

Outstanding feedback!

AJ,
That was my thought as well. My Kawasaki dealer is closed on Mondays so I'm waiting until in the morning to check the price for the shift star. Eric states in his book that Kawi went too soft on the spring in '97 and the bikes were popping out of gear, so I'll have to be careful with that. Check out the link azcourt posted.

bigred455,
We share the same pain. If the shift star isn't very expensive I'm going to try it. Check out the link azcourt posted. BTW, I installed a 50 tooth rear sprocket to help me stay out of first as much as possible, but in the tight stuff I still need it.:ugg:

azcourt,
That's what I'm talking about! Thanks for the post. Once I found the hidden links (first time on thumper talk) for the pictures, it was explained perfectly. He may have taken off a little more material than I was planning, but we are on the same page.

Hopefully we'll get some more discussion on this topic. Thanks again for the great input and I'll keep you posted.

Scott

 

[davidco]

Shift Star

I recommend removing the shift star and shift forks and polishing them. Then, try one size larger boot size on shifter foot!;)

 

[bscottr]

:p :p :p

davidco,
Junior member? What's up with that? You new here?

Wouldn't you also polish the shift drum? Oh, you polished everything for me, that's right.

I take that back. You forgot to polish my boots!

Sorry guys,
Scott

 

[bigred455]

LOL scott just read the modificaion,it does make alot of sense,let us know how you made out.

 

[bscottr]

Shift Star Price

FYI,
$53 retail :( :think Seems high!
$29 my price :D :confused: That's better.

It's dremel time.

Scott

 

[bscottr]

It Works....

Thanks to Eric I'm up and running again. If you want a broad power band, I highly recommend Eric's Mo Better porting and mine's on a 265 kit. :aj:

Anyway, back to the issue, here's what I found.

The points on the shift star for neutral are actually slightly shorter than the other points (.03). I believe it's the shape of the neutral points that makes them appear taller. As I said in my original post I (actually a buddy) polished the contacting points of the shift drum, shift forks, the shift star and the mating surfaces of the shift pawl and shift shaft. This made the shifts of 2nd through 5th very, very smooth. It’s not at all hard to do, you just need a polishing wheel on a bench grinder. However, I don’t believe it helped much with the hitting neutral problem.

The fix for hitting neutral is with the shift star. Looking at the “ramps” for neutral on the star that the wheel follows, you’ll see that they are very steep, more so than the ramps for the other gears. That’s the problem. Changing the shape of the neutral ramps to closely match the shapes of the other ramps is what we did. This does require that the height of the neutral points be decreased slightly. Again, this is not hard.

For a great description and pictures of the process follow the link in azcourt’s post above or follow this: http://www.thumpertalk.com/bike/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=10&t=002432&p=

This is almost exactly what I did, except I didn’t remove quite as much material as he did. I will say that finding neutral now requires smoother (slower) movement of my left foot. However, it’s not hard to find.

All shifts are now silky smooth and shifts from 1st to 2nd and 2nd to 1st are the way they should be. :cool: Hopefully this will help anyone with the same problem I had. AZCOURT, thanks a ton for posting that link, it made a world of difference.:D

Scott

 

[azcourt]

Your welcome.

Now I guess I'll have to try it on my YZ 400. Wish me luck :)

 

[bscottr]

Another Ride Report

AZ,
I believe you'll be glad you did if your YZ shifts like my KX did.

I rode nearly 40 miles yesterday, most of it in a lot of tight stuff where I used 1st and 2nd often. The shifts were very much improved, nothing like prior to the modification. Before I needed to use the clutch and really needed to concentrate on making a very firm shift into 2nd. Not anymore, I can now shift without the clutch and it feels just like the shifting from 2nd on up. Except now that's even better with the polishing.

If you make the mod, I recommend that you polish all the contacting points of the shift star and the contacting points of the shift shaft and shift pawl. The nice thing is you don’t need to split the cases to do it and you can do it in less than two hours, assuming the YZ is like the KX. Of course if you polish the shift drum/forks, that’s a different story.

Keep me posted and drop me a line if I can help. Again, the directions you posted were outstanding, but note in a later post the fellow says he may have gotten happy with the file. Concentrate more on the shape than the height. The height will be decreased, but only enough to accommodate the shape of the slope. Good luck!

Thanks Again,
Scott

 

[azcourt]

Good news, my cases are already split. I have been waiting on parts for nearly 6 weeks. I blew it up missing a shift :scream:

 

[bscottr]

Ever tried these guys?

AZ,
Have you ever tried Parker Yamaha? The service and prices we've received have been great. I'm not sure how your local dealer is, but if you want to check these guys out try www.parkeryamaha.com.
Sorry to hear about the blown motor, I can relate. I was lucky to have a backup bike while my KX was down. I didn't realize how expensive the down time would be; new pro tapers, bark busters, bar mounts, grips, forks revalved, fork springs, skid plate, graphics, chain, sprockets, flywheel weight, etc. Stuff I needed to do anyhow, but man when you do it all at once….wow. :scream: The cheap part was having Eric do my top end.:confused:
Since the cases are split, might as well warm up the polishing wheel!

Scott

 

[azcourt]

I can relate, all this down time got me a BBR kickstarter, Hebo clutch, new bars, fork seals, bark busters, fork gaurds, stabilizer rebuild, swing arm bearings, not to mention the 426 rod, head, piston, cylinder, wr transmission, shift forks, bearings ect..ect...ect. I am doing the work myself this time, except for the crank rebuild and valve job. The shop doing that stuff gives me a good enough discount to make the wait worthwhile.
I borrowed an XR 650 last week...this is the first bike I have ridden that weighs more than I do...what a beast.

 

[bigred455]

Hey AZCOURT,great details on the shift star mod.When I had my cases apart to do the bottom end me and my buddy tried to figure it out, if you are turning from 1st to 2nd or 2nd to 1st you can feel the tension from the ramp's.When it makes it over the point it just drop's down with alot of tension into neutral.It makes alot of sense to take some of the ramp off so it won't be so easily pulled down into neutral instead of advancing to second.Me and my buddy tried to figure it out with a softer detent spring,but that did not do anything.My clutch case is coming off this week.I will let you guy's know if i had success also.Thank's for the great tip.