Author Topic: Is TL125 the same mech's as SL/XL engines?  (Read 2183 times)

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Offline John Orchard

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Is TL125 the same mech's as SL/XL engines?
« on: February 28, 2022, 08:03:16 PM »
As the heading says, the TL125 trials iron, anyone know if the engine internals are the same as the SL/XL125's? Would the TL run a heavier flywheel, different cam timings, gear ratio's?
Johnny O - Tahition_Red factory rider.

Offline sleepy

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Re: Is TL125 the same mech's as SL/XL engines?
« Reply #1 on: March 01, 2022, 10:45:12 AM »
You ask good questions. From the manual the gearbox spec is different to the SL125. First and fourth are the same and the primary reduction is the same. Comp ratio is 8:1 compared to 9.5:1.
I have a TL125 but I can't remember comparing cams or flywheels.

Offline bazza

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Re: Is TL125 the same mech's as SL/XL engines?
« Reply #2 on: March 02, 2022, 11:27:10 AM »
On the TL250 flywheel is lighter than the XL250
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Offline sleepy

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Re: Is TL125 the same mech's as SL/XL engines?
« Reply #3 on: March 02, 2022, 05:26:08 PM »
On the TL250 flywheel is lighter than the XL250
That is the weirdest thing with those. You'd think a Trials bike would have had a heavier flywheel but then again a TL250 is a terrible trials bike so it isn't surprising. Just done some repairs on a TL250 head and I was surprised to see the inlet port was 26.5mm compared to XL at 32mm.

I think the 125 flywheel is the same as is the head and cam but it's been a while since I've had a TL125 apart.   

Offline pokey

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Re: Is TL125 the same mech's as SL/XL engines?
« Reply #4 on: March 02, 2022, 05:45:51 PM »
At low RPM air velocity makes power and high RPM its more air for power and those engines have larger valves with a higher lift. thats a basic difference with V tech engines is the second set of cams to increase Lift. This would explain the 250 valve sizes.
 The cam, piston and the crank on the TL125 have a part# only used on the TL. Valves are the same as CB so pretty common and probably the same as other 125/100 models.


Offline djr

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Re: Is TL125 the same mech's as SL/XL engines?
« Reply #5 on: March 07, 2022, 02:06:51 AM »
This is going off topic a bit, but a friend who knows very little about bikes purchased a TL125 without knowing it had the wrong CG125 pushrod type engine fitted.
{ it looks to be a straight bolt in swap, with no mods visible }

when I first saw the bike and pointed this out to him , he had already had the bike a while and was pleased with how it performed.

He was disappointed , and contacted the seller , who was just as clueless and unaware the bike had the wrong engine.

My friend was going to look for a correct engine , but has now decided to leave the CG engine in the bike as it performs well enough for his needs, plus spares are cheaper & easier to obtain { the only downside is the reduced resale value of the bike}
 
Obviously the CG top end parts would be no use on a TL/XL/SL  , but maybe some bottom end / gearbox parts may interchange ?
{ I dont know personally, but could be worth checking for matching part numbers }

Offline Tex

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Re: Is TL125 the same mech's as SL/XL engines?
« Reply #6 on: March 07, 2022, 12:05:27 PM »
Quote
the TL125 trials iron, anyone know if the engine internals are the same as the SL/XL125's?

The CT125 might be worth looking at as well.

Tex