GT big block experiance : New GT crank info added

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eden
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GT big block experiance : New GT crank info added

Postby eden » Fri Feb 28, 2014 8:35 pm

You may know I've been running one of the prototype barrels in my GP since last March or April along with a good friend of mine, Mik, who has been running the other prototype barrel in his GP.

Miks setup was as standard using 58mm stroke and just bolted on, I wanted to run a 62mm stroke on mine so had a little bit of work to do before getting it on the road, I also wanted to use the same piston that I use in my home tune 245. However Richard didn't want the barrel taken out to 71mm straight away and would only agree to me taking it to 70mm.

As I like to do things as cheap as possible I used the 62mm tino crank that had fallen to pieces on me several times in my home tune 245. The piston Richard wanted me to use had an 18mm pin so the crank had to be split and rebuilt to take a suitable rod. The crank came back with a welded big end and a warning that the pin wasn't very tight lol. The engine casing I used was the old casing I used to use for my 225 cast tune over 20 years ago which had been destroyed when an asso inlet skirt broke off at full chat in 3rd gear and exited through the back of the crankcase. The casing had other problems that needed welding too, but Guy Topper did a fantastic job getting the casing back to being usable.

While all this was going on Mik was ridding around on his NOT running it in lol and loving every minute of it. It pulled from low down really well due to the reed and revved on nicely even though it was running a big bore exhaust. The exhaust was a few years old and the extra power soon finished it off. After using an old JL4 I had for a week his new Franspeed race arrived. The expansion transformed the performance as you would expect, it still pulled extremely well in low revs but now revved out and had a nice kick as it hit the power band. It clocked 82.7mph on gps and still didn't have more than 200 miles on the barrel. his gearing was 4.8 final drive.

My engine parts came together and I pondered a few barrel positions giving different port timings before deciding what to go for. I had a bit of a dilemma due to the transfers being a tad higher up the barrel than I would have liked meaning the transfer durations were a bit long what ever I did, bare in mine I didn't want to machine anything of the barrel, top or bottom and didn't want to do any porting to begin with. I wanted to try it as is and then make changes methodically over the year.
When I got it on the road I was amazed how well it pulled at low rpm in top gear, the only way I could describe how it rode was to say, "it's like ridding a standard GP when your taking it easy and like a full blown tune when you open it up". Even though it didn't feel as fast as my 30bhp home tune it was much easier to ride and fast enough to keep up with the other guys on TS's.

I had only had it on the road about a week and we took both scooters on a dyno, we rode there and on the way mine felt a bit sick. The dyno results showed that mine was a bit sick. Miks in standard format did something like 24bph ( Richard will remember the actual figure )and mine only did about 21bhp.
On inspection it looked like the flywheel was oscillating so when I got it home I stripped it down to find the Tino crank had cracked the pin weld and twisted.

It was expected tbh as the pin was loose when the crank was built. From then on the engine was going to be a 230, with a 60mm x 107 crank that was available.
The rod in this crank was 16mm so I decided to try using a TS1 piston, not a new one mind as I only wanted to try it, a good mate gave me an old used piston that came out of his TS the year before. Also for a laugh I decided to try the kit with very long exhaust and xfer timing. I raised the exhaust port by 2mm and set the barrel to sit with the piston 1.3mm down at TDC and no head gasket giving of the top of my head something like 194 exhaust and 139 transfers, way too long but while your f@@king around why not try it lol.
I ended up ridding it round the rest of the year like that, it still pulled well at low rpm but didn't hit the power band till over 7k rpm then pulled your arms off for 1k more rpm lol, this set up eventually killed the clutch on the way back from the four nations, it got me home but I was at the back for the last 50 miles nursing the clutch while everyone else f@@ked off :lol:

MIks ran well all year and a couple of months ago he fitted the new bridge port version of the kit. My GT has just come of the bench after changing the port timings to a more reasonable 189 133.

Last weekend while ridding back from Burton I was ridding my 245 cast engine in the winter model following Mik on the bridge port version. He was ridding for a few miles at one point at 8200 rpm in top into a medium headwind on 4.8 final drive. I could only just keep up with it............... to say it goes well is an understatement especially considering its only 200cc.

Anyone looking for a easy to ride fast kit who doesn't consider one of these kits needs their head looking at!!!!!!!!!!!!!!!!!!

Ill add some video and stuff some other time, pubs calling now.

Any questions, fire away :D
Last edited by eden on Tue Jul 28, 2015 3:53 pm, edited 1 time in total.
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GP240
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Re: GT big block experiance

Postby GP240 » Fri Feb 28, 2014 9:53 pm

Thanks for sharing Eden, good to get a view of a kit/engine that has done the miles, nice way of testing it (lucky get) lol.

cheers Boo.
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eden
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Re: GT big block experiance

Postby eden » Fri Feb 28, 2014 10:02 pm

tbh there were two reason I used old crap I had lying around the garage to build the engine I put the kit on to.

1: some people out there will buy the kit and just slap it on their existing engine with out upgrading anything else, the engine I used resembled such an engine block.







2: this is the main reason I'm tight
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Andy Pickering
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Re: GT big block experiance

Postby Andy Pickering » Fri Feb 28, 2014 10:04 pm

eden wrote:






2: this is the main reason I'm tight


Tbh that was the only conclusion I came up lol

Sent from my GT-I9300 using Tapatalk
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Mr G in NYC
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Re: GT big block experiance

Postby Mr G in NYC » Fri Feb 28, 2014 10:42 pm

Looking forward to picking mine up in UK
and hand carrying back to NYC for a Fit
and fettle summer project …… :D
Eden you C2C this year ?
best rgds
G.
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eden
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Re: GT big block experiance

Postby eden » Sat Mar 01, 2014 1:22 am

Maybe Mr G, got a lot on scooter wise this year and April is crowded. if I do I wont be racing, ill just be doing it for the ride and a chat :)
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Mr G in NYC
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Re: GT big block experiance

Postby Mr G in NYC » Sat Mar 01, 2014 2:11 am

Sound…i'll ping you nearer the time……just booked my airline
ticket….so its on for me :D I'll pick your brains on the kit
as well………… 8-) best G.
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Re: GT big block experiance

Postby eden » Sat Mar 01, 2014 5:43 pm

We have both been out all day on our GT's today, great fun.

Mine runs much better now with its more reasonable port timings.

My helmet cam has been working on and off over the last 9 months so I don't have much footage currently, however I have just ordered the part I need for it so once it arrives I'll do some vids to upload.


Ive just dug out what I can find from last year that relate to the GT200,


These videos don't show much and the sound is bad on them due to the camera starting to f@@k up, as I said ill get some good footage over the next weeks and months showing them being ridden in all sorts of conditions.

In this one im following Mik and his Mrs who are on his GT kit, im on my home tune cast 245........... following Mik from 2:10, he didn't have many miles on the kit at this point.




This is a video of the first few tentative miles on my GT kit with the 62mm stroke last year.

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Re: GT big block experiance

Postby Morgan » Sat Mar 01, 2014 6:53 pm

Eden

Do you have any experience with the Avanti and MB/BGM kits.

With the GT kit these three seem to be going for a similar market, just wondering who has an tried all 3 and can comment on pro's and con's
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Re: GT big block experiance

Postby rosscla » Sat Mar 01, 2014 7:37 pm

You running that GT on lawn mower oil?
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