Rotary valve help

WIESEL

WIESEL

Been Around the Block
I have been having a heck of a time getting my ts90 tuned in and came to the conclusion that my rotary valve system is on the Fritz.

I thought maybe some of you might have some pointers for me.:))
I bought all new parts last night and they should be here mid week.

Thanks
u4yve8a3.jpg


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Those things all ran rich from the factory. Drilling holes in the air box helps, but you may have to go a jet leaner than the stock jet. Also, there is a spark arrestor in the muffler baffle that gets clogged with carbon. You can punch it out with a hunk of steel rod. It will never tune if the baffle is clogged.

I seriously doubt your rotary valve has a problem.
 
I thought the same thing but, after doing all you mentioned on top of brand new crank seal, points condensor, multiple jets, multiple float levels, and new plug.
I think it's the problem.
What you can visually see of it looks a little boogered up and it blows a fine mist out of the carb at times.
The motor has a fresh top end with great compression and little to no crank play.
I wonder if has been freshened up with no rotary valve inspection.

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There is enough overlap in the rotary valve timing that certain conditions, such as low RPM with heavy throttle, you will get some reversion out of the carburetor.

Make sure you check that baffle. It will have you tearing your hair out trying to tune with a clogged exhaust.
 
The baffle is removed and currently soaking in my parts washer.
What would be the symptoms of a wore rotary valve and how long do they usually last?


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I've never heard of one wearing out. They are thin spring steel.

Look down the baffle, and there is a plug in about the middle. Soaking it will not clean it out. Punch out that plug with a steel rod. It won't affect the sound much. That is a US Forestry approved spark arrestor. We always punched them out at the 500 mile checkup, because they ALWAYS clog up.
 
Could it be out of time?

I ran it with the baffle off with the exact same results.

I haven't found any good reads on the ts90 rotary valve but, one video of a bad one with comments saying that was the culprit.

I have found some info on the gp100 failing with similiar issues.

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they can get worn out from ingesting mud and dirt
it needs to be flat and free of any large grooves,i have seen them worn to a knife edge and bits braking off
make sure it is timed correctly and in good shape
 
Some pictures of the rotor.
yredape3.jpg
ehede4aj.jpg

The pictures do not show the severity of the warpage and pieces missing. Also there is deep grooves in the cover and backing plate and around the inlet on the backing plate is really chunked out.
aqytu2e9.jpg


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looks ill,in order for the intake charge to be moved around with the required efficiency a gooder seal on the plate is needed
i would get a new disc,remachine the surfaces and set the tolerance to specs(disc to housing axial clearance,side play in plain english)
 
Thanks bud..
I have a new backing plate, rotor and, cover on the way.
Would I need to do any adjusting with all new parts?

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I don't think you should need to adjust the clearance with all new parts...
that is great that you could get them !! ;) make sure everything upstream is nice and clean, air duct, filter and cage etc ;D
 
xb33bsa said:
that is great that you could get them
Click to expand...

In my experience, Suzuki is the best of all the Jap manufacturers for having parts for the old bikes. Reasonably priced, too.
 
Thanks for the help guys..:))
I will keep you updated with the progress.
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Finally found time to install the new parts. With the new parts and a little float adjustment, I thought, it was time for a test ride...
Then, I lost spark....
So, time to inspect my points, condensor, and coil.

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Anyone know the exact point gap spec for this bike?

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If I recall correctly, there is no "exact" point gap spec. The timing is set by tweaking the point gap. It should be something like between 12 thou and 18 thou. Now mind you, I am dredging this up from my old brain from the 70's when I worked on these bikes new, so I may not be remembering exactly.
 
Well, I fixed my spark issue and she runs real good on top and idles.
I am thinking I have the carb dialed in but, I think it needs some tweakage to the timing.
It is kinda hard to start and doggy on bottom.
I have the point gap at .014.
Its really fun to ride and likes to wheelie.8)

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Does anyone know the correct placement of the rotor on these.
I tried it where the original one was and with the it aligned with the woodruff key.
It seems better with it aligned with the woodruff key.:-\

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