TS125C - Low speed expectations

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Paul in NZ
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Re: TS125C - Low speed expectations

Unread post by Paul in NZ » Mon Jul 16, 2012 1:52 am

Air leaks on the induction side OR crankcase / seals. Also whats the fuel flow like? Is the tank venting properly?
He who hears not the music thinks the dancers mad....

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Zunspec
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Re: TS125C - Low speed expectations

Unread post by Zunspec » Mon Jul 16, 2012 2:17 am

Hi Paul,

Tank venting and flow are OK. Good point on the crankseals, although the were replaced during the re-build. I made a slight adjustment to the ign. timing tonight, it was a bit retarded so i'll give it a run tomorrow and see if it makes any difference. It has been running great over 6000 rpm but having watched a few vids on YouTube it is obviously not running to spec before that. The top end leanness has come as a surprise which could certainly point to crank seals, with luck they can be replaced without splitting the cases.

Cheers Zunspec

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Room101
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Re: TS125C - Low speed expectations

Unread post by Room101 » Mon Jul 16, 2012 12:16 pm

My 2c

I have no idea how they are supposed to run but I’ve had similar bikes (and have a Kwak 125 now)
These tiddlers are great fun when they are running well. I have found they are super sensitive to having the mixture set spot on. Have you tried the Gunsons Colourtune? This thing works for me, I think you should have two mixture screws, one for the low revs and one for high revs, do both. Setting the screws real slowly to exactly when the flame changes colour makes such a difference to even an eighth of a turn out. If you have or can borrow a colourtune plug it’s a quick thing to do.

I recently had to take the Kwaks carb apart and clean it three times it had not been run for a while. The jets had got gummed up. I was a bit norty and had to use a fine pin to clear the secondary jet (which are normally held in a deep well and have a very small hole, so they are a great crud catcher) on my third attempt. Then it ran real nice and went like stink. Before that it felt chocked like a dirty air filter, but it was my secondary jet gummed up. That would for sure account for low speed pickup going out of the window!

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Room101
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Re: TS125C - Low speed expectations

Unread post by Room101 » Mon Jul 16, 2012 12:21 pm

if you suspect a blocked secondary jet (whucg is my bet!) then clean the jet first the do the colourtune. when you have teh carb apart set the float height tab with a steel rule just in case thats set wrong and starving the engine on acceleration. On old bikes those copper tabs get tired. The float pin cone rubbers also get a tiny groove worn in them where they hit the seat, that makes them stick slightly and hold the float slightly.

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Zunspec
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Re: TS125C - Low speed expectations

Unread post by Zunspec » Mon Jul 16, 2012 12:44 pm

Good morning 101,

Thanks for the input.

I've pretty much made sure that the Main and Pilot jets are not blocked, they have been cleaned with carb cleaner and compressed air several times now. The float height was checked using a vernier caliper and is within the tolerances specified in the w/shop manual. I usually set the Pilot air screw for best revs at idle (or just above) believing that this will be the best mixture, but I will set it back to the standard 1 turn out.

Checking for air leaks I discovered the barrel hold down nuts were not tight so these have been addressed, it's possible it was drawing in air from underneath the barrel/reed valve to c/case interface. I just gave it a run and was pleased to see the plug showing signs of "tan" colour which bodes well. It was still hesitant at low revs however so something still needs sorting.

I will continue to fettle and report back.

Cheers Zunspec

Coxy
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Re: TS125C - Low speed expectations

Unread post by Coxy » Thu Aug 09, 2012 10:27 pm

Try to richen up the mixture as the Fuels that were available when these bikes were new were not as dense as modern fuels,Specific Gravity is the Technical term for Fuel Density and thicker fuels to use laymans terms do not flow as well through fixed jet sizes therefore modern thicker or Denser fuels will run leaner than the fuels available when this bike was new.

Lean two strokes are not always faster before they blow up as in the old wives tales,By the sound of it it is probably lean on the pilot jet and make sure the float level is spot on to spec as that will adversly affect mixture strength as well.
Suzuki's of that Era usually had a 10mm Hex bolt on the side of the carburettor body that you removed to find a spotfaced dot on the Carb Slide that you use to line up the oil pump setting as well,so check that is correct and do not forget many modern two stroke oils run much lower percentages than the older mineral based two stroke oils and modern semi or fully synthetic oils may need the settings backed of somewhat or they will actually over oil the engine and make it run poorly.

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Zunspec
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Re: TS125C - Low speed expectations

Unread post by Zunspec » Thu Aug 09, 2012 10:57 pm

Hello Coxy,

Thanks for the input. It runs very well once past 5.5k revs so I guess the needle jet and main jet are working well. I'll will try the next size up on the Pilot jet and see how it goes.

I have set the oil pump using the little dimple on the slide as I am running old style Castrol Acteavo (sp) oil not a synthetic but will bear that in mind.

As the Triumph returned from the Hunters Lodge bike night today with a front wheel puncture and copious oil spewing from the breather (the trial using the old pistons and rings = Failed) that will be going back on the bench and the TS125 will get a bit more running. I'll report back on progress.

Cheers Zunspec

Coxy
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Re: TS125C - Low speed expectations

Unread post by Coxy » Sun Aug 26, 2012 1:47 am

Just remembered a little trick we used back in the day tuning Suzuki RM's as I worked on Suzuki's Australian sponsored Race Bikes we found that retarding the reed timing by using an additional set of reeds on top of the stock ones gave better bottom end power,Careful measurement and study of the PE 250 Enduro bike engine compared to the RM 250 led to this discovery,Might be worth a look for the TS125 C as well being yet another Case reed piston port engine.

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