GP Street Racer Build

Post pics & videos of your scooter, projects you're working on, a lovely Vespa that you saw at a rally, or anything else scooter related.
paul d
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Posts: 312
Joined: Thu Jun 30, 2011 10:00 am
Main scooter: T5 172 Tv 240
Location: Galway Ireland
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Sun Jul 26, 2015 7:04 pm

I agree with you as regards the grip, they got that part very right. Just looked at the pics again...great job!

simon_t
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Posts: 15
Joined: Sun Feb 16, 2014 6:33 pm
Main scooter: LAMBRETTA DL125
Location: Tamworth
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Sun Jul 26, 2015 9:04 pm

Looking good mate... :D

Rs fruitbat
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Posts: 87
Joined: Sun Aug 24, 2014 10:11 am
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Sun Jul 26, 2015 10:35 pm

Nice job ;) is your user name a clue to your rally car interest ?

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T5-190
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Posts: 689
Joined: Thu Jan 08, 2009 3:25 pm
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Tue Jul 28, 2015 7:40 pm

Very nice indeed, good build. Love it.

Boreham
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Posts: 162
Joined: Tue Feb 05, 2013 7:58 pm
ebay user ID: rsboreham
Main scooter: GP225
Location: Leicester & Dusseldorf
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Sat Nov 14, 2015 4:48 pm

Update:
Changed the tyres for Conti sports, good recommendation!
Also after running in the engine was quick but not quite the 'grunt' i was expecting, hard to put your finger on but not quite enough??? (i know!)
Then i bumped into Harry from Pro-Porting, after a bit of reminiscing (he built previous scoot engines and RD350 race bike back in the 90's) he suggested i pop round the workshop for a cuppa.
I stripped the engine and dropped round, he said if i was prepared to spend the day he would do any required work whilst i hung about, which was interesting as there was so many new goodies about (his own brand new reed inlet, new clutch design and the legendary 290 barrels)
His main comment was the Monza barrel has conservative transfers, so set to work...

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The transfers on the Monza barrel are quite close to the edge of the crankcase and as Harry was going to work on these the mouth needed tig welding to give sufficient sealing face.

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The crank housing was then trenched to allow room for one of his 'special' cranks!, final spec was 62x110 with Yam rod, all fine balanced and tig welded, a real work of art.

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Harry the set to work on matching the crankcase transfers and porting the barrel, watching him at work was interesting, the fine tolerances with the diamond tipped tool was fantastic, worryingly was the sheer amount of alloy coming out of the casting!! ( i did say 'do what you feel is ok')
Transfers opened, the exhaust was further worked and inlet profiled and flowed for the larger Yam reed block and MB inlet.

Dry build time...

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New inlet and upgraded to a Mikuni TMX 35

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The initial measurements gave the port timings of
Exhaust 94/188o
Transfers 63o/126o blow down 31o
Squish 1.2mm with 3mm packer and 2 x 0.75 gaskets.

The crankcase was then coated in black and the chain case carbon dipped.
Initial runs on the dyno felt good, although had a major issue with the new BGM flywheel rolling of the ramp and cracking a couple of fins....! a new AF mid weight later and jetting ended up at 22.5 pilot, EN56 needle on 3rd clip and 315 main.
The comment was the Franspeed 3 pipe was holding back as Harry commented it should be good for 9500-10,000rpm! and the pipe was really aimed at 7000, the ideal solution would be the Franspeed race but on the road it feels great, very torquey with an almost Yam 80's like power band at around 5500rpm.

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mick1
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Posts: 1527
Joined: Sun Dec 04, 2011 7:43 pm
ebay user ID: saxonleaf
Main scooter: Li Avanti 225
Location: York
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Sat Nov 14, 2015 5:21 pm

Cracking build and well documented.

Out of interest what increase in HP have you achieved ?

and how did you register a new frame and get a "J" plate

Boreham
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Posts: 162
Joined: Tue Feb 05, 2013 7:58 pm
ebay user ID: rsboreham
Main scooter: GP225
Location: Leicester & Dusseldorf
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Sat Nov 14, 2015 5:54 pm

mick1 wrote:Cracking build and well documented.

Out of interest what increase in HP have you achieved ?

and how did you register a new frame and get a "J" plate
It ended up a shade under 26hp, the plate is a private addition.
Cheers

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Toddy
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Posts: 4991
Joined: Sun Mar 08, 2009 12:01 am
Main scooter: Lambretta Series 1
Location: East Yorkshire
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Mon Nov 16, 2015 7:28 am

Lovely Scooter and nice Update :D
As my Dad used to say "Each to their own lad"

sydduckett
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Posts: 2166
Joined: Wed Jan 14, 2009 12:21 am
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Mon Nov 16, 2015 8:41 pm

I have a cyclone in my RB and I love it. I had to use a camera phone when setting it up and it wasn't the best view to be honest. I think from memory I had about 3/4 of the gear and tree meshing. I haven't had any issues but the engines out and in pieces at the mo so I'd like to try and get more of the faces meshing.
I'd be interested to know where you drilled the end plate so you could see better and what the engineers did by way of getting the gear and tree in line.

thanks
Sef.

Boreham
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Posts: 162
Joined: Tue Feb 05, 2013 7:58 pm
ebay user ID: rsboreham
Main scooter: GP225
Location: Leicester & Dusseldorf
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Sun May 07, 2017 3:18 pm

An update from changes over the winter, upgraded to the franspeed race which really releases the power of the kit, also struggled to jet the TMX in the mid range, tried every combination of jets and could not quite get it right.
Changed to a VHSH as supplied with the Super Monza kits and setup was much easier and actually feels better on the road, lots more mid range and wants to rev on, this carb really does like smaller pilot jets, finally ended up at 44 and still 4 strokes slightly off idle but pulls even in 5th.
Also added the Kytronik to help on the timing.

The next step was the panel work, was intending to water cool the head so turned to Chris at GRP who made a superb set of vented panels and a very trick set of leg shields with combined glove box.
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