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· Registered
43 Posts
Discussion Starter · #1 · (Edited)
We have owned my wife's 1987 TW200 since 2015 at 2,120 miles and it has been very reliable. It just always works. Now at 8,580+ miles.

July 2022 - pulled out of storage, primed carb and it started instantly. Installed new chain and sprockets to slightly taller gearing from 14/51 to 14/49.

Early August 2022 started having issues running doggy, the little engine has to work hard with a lot of wait to get to 45 - 50 mph with slight pulse in engine at higher revs, almost like a miss. Also had an off idle bog.

Went through the carb and cleaned out everything. Needed to clear out partially clogged pilot jet - off idle bog resolved.

Fuel flow from tank is fine - preventatively added inline fuel filter between tank and carb.

At that time I discovered mice had chewed some wire insulation up over the battery and some of the snorkel end over the winter. Reinsulated wires and cleaned out some seeds stored by the tenants in front of the air filter. Nothing got past air filter element.

Spark plug gap was a little out of spec at .030 - set to .025.

Intake valve was .0045 - Set to .003

Exhaust valve was .006 - Set to .005

Tested bike without air box filter and cover.

None of this had made any difference. Last week my wife did notice that at one point the bike 'cleared up and ran fine for a bit'. Then it reverted back within a few minutes.

I am now suspecting the infamous 87 CDI. I removed it and put it in the freezer. Hooked it up and tested. No change. Wacked it with a screwdriver handle. No change.

Is there additional troubleshooting to conclusively confirm the CDI is the culprit before I make a significant irreversible electrical component purchase?

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· Registered
43 Posts
Discussion Starter · #16 ·
I received TW-brian's 87 CDI loaner in yesterday's mail. Huge thank you to Brian for making that possible.

Swapped it into the Tdub this morning . . . no change. Still weak running and difficulty getting up to 35-40. So it appears the CDI has been ruled out as the possible cause.

When disassembling carb I could not figure out how to remove main jet needle to inspect for wear. DR350 pumper carbs can have run-ability issues due to worn needles. Its the linkage from the top of the TW carb that has me stumped.

I recall reading some time ago a TW200 owner swapped out for a CV carb. Possible solution?

· Registered
43 Posts
Discussion Starter · #17 ·
Today, things have improved quite a bit due to of all things, gas cap not venting. The tank held vacuum in it for 15+ hours! Ran the bike with the cap loose - big improvement. Got it apart and cleaned and now that's good even when sealed and locked.

Now going to check float / fuel level as that measured too high initially, so I lowered it. Now I'm wondering if the vacuum in the tank wasn't messing with those initial readings and I adjusted it based on a false positive.

I am becoming more hopeful after verifying multiple things with no solution in sight.

· Registered
43 Posts
Discussion Starter · #19 ·
90% there. Every time I found something out of the norm or out of spec I thought that would be it.

I tried, checked or repaired the following, all with no change:

wires with chewed insulation above battery
Spark plug gap was wider than spec
Fuel flow good - inline filter added as precaution (flow still good)
Boots passed WD40 test - no rpm change
air filter cleaned - re-oiled
air filter and cover removed entirely
valves checked - in spec - but adjusted to middle of spec ranges
CDI swapped out for a good one from TW-Brian
minor oxidation on connections in connector block to rectifier - removed and lightly sanded / cleaned.
Cylinder compression measured 157 multiple times with screw in type gauge
(spark plug dark black and sooty after idling warmup prior to compression test)

carb removed and cleaned multiple times
'coasting enricher' diaphram checked - no holes or tears

Adjusted float bowl level in carb bowl as measured out of spec - Need to recheck that now that vacuum from tank is gone.
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