GP 125 - TS1 engine. Fully rebuild

[FraH2O]

I made some works and experiments. First was to fit mirror. I bought a BGM mirror to fit on Vespa toolbox (I don’t want to fit on lambretta body). Before to fit the mirror, I painted I to cover the fake carbon trim.



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I made the hole on the toolbox side.




I think that’s looking good. It’s so small, but it’s a good mirroring look.


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Second work: the Koso Rev counter. Another hole on the toolbox.




I fitted the rev cable following the original electrical wiring. Looks good and hidden


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The most important work was to test the Franspeed race exhaust




The recommended timing spec for this exhaust is 190° (exhaust port) and 130° (transfer port) My barrel is standard (just made the transfer case matching). I wanted to try the differences with my original spec (carb , barrel and gear ratio)

JL4 vs Franspeed Race






The fitting was fast. JL4 and franspeed have the same barrel’s flange




My only test is the road. I don’t know nobody near to me to test my engine on test bench.

My spec is:


Ts1 standard (matched transfer) 184° exhaust and 130° transfer port
Mikuni tmx 35 with Ramair filter (270 main- 22 pilot)
Pacemaker gearbox with 47/18; 4,80 final ratio
As I read about it from GpKevo, the franspeed is quieter (especially when is warm). The manifold have more ground clearance than JL. But the JL look is more racing than Franspeed




My impressions were: engine’ progression is linear (JL is more nervous in his progression). I pushed the engine to high rev to check the limit.
The Franspeed stopped my engine before my JL4. I did not need a test beanch to feel this.
I decided to fit my JL4…I think to develop my engine around this exhaust



Yesterday i went to scooter meeting near home. 160 running miles.
Near location was a track famous for karting and drifting




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Next month I’ll try the 4.70 ratio. I think that my engine can pull this ratio.

[FraH2O]

Some news and some solved and unsolved problems.

I decide to came back GP rear light.


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I think it's looking better


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Waiting the fitting of LTH manifold, i try to solve this problem



With Dell'Orto VHSB never had this trouble, Mikuni make me crazy.



Another possible tip that help the mikuni unfastening is this:



Running board scrapes the carb



I cut the running board.


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I fit also an on O-ring on Mikuni to prevent the unfastening. For this trouble Dell'orto is long better

And finally arrived Tassinari VForce 4 and LTH


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Just little mod


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Now I need to modify the lth manifold to match the port with reed. I think I’ll weld and re-shape.

Some pics from a scooter meeting in this past weekend


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That's all.

[Toddy]

Great Work Mate , i like the GP Rear light unit better

[FraH2O]

Great Work Mate , i like the GP Rear light unit better

Thanks Toddy!

[FraH2O]

This past weekend i completed the Tassinari reed conversion.

I had many fear when arrived to this point..



After 2000 km running (1400 miles) the barrel is in mint condition. The replating work is good.



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Also the piston is in good condition. Just little dirt: I run at 2,5% Motul 710 full synth to prevent any damage at highest rpm.




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I started to modify the inlet port to fit the Vforce





Dremel helped me to made good matching




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Inside the reed is ok.





I matched manifold with inlet surface reed




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Finally i polished the exhaust port






My only doubt was the clearence from frame. Tassinari is higher then RD




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Clearence is good, now just find flex hose to fit Ramair filter




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Engine speed is more faster specially at low rpm.

Now I’ll just change the 47 clucth crownwheel to 46. The ratio will be decreased from actual 4.80 to 4.70. I think my engine can push it.

[FraH2O]

Yesterday in the afternoon was impressive hot weather.

I was sure that my engine could pull a longer ratio

I change from actually 4.80 to 4.70




The JL4 is for me the best overall exhaust, and i’m sure that can pull the 4.70 ratio

I stretched my Lammy to avoid draining the oil.





Removed the chain tensioner.





I Changed the 47 crownwheel with 46 and fitted the reverse pull chain




Test ok: my engine push easily the new ratio without problem. I fell the speed increasing.

In this weekend I’ll test with gps.