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PostPosted: Sun Jul 01, 2018 12:31 pm 
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Still in the Driveway

Joined: Sun Jul 01, 2018 12:27 pm
Posts: 3
Country: Poland
Bikes owned: Yamaha rd250
Hello,
Newbie here and wanting to know if I can safely mount a 380 motor on a 250 frame? Any help much appreciated!


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PostPosted: Sun Jul 01, 2018 1:43 pm 
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Road race school

Joined: Wed Jul 10, 2013 12:04 pm
Posts: 800
Country: England, UK
Bikes owned: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
Hmm. Interesting. Not sure how feasible it is. Sure someone on here would know. Try asking Dollydog, he's done a few gt250s and is no stranger to fitting odd engines in frames.
I know you'd need to upgrade the stock sidestand. The GT380 is a lot heavier than the GT250 lump and the standard side stand bracket is puny and known to crack the welds where it joins the frame.
You'd need GT380 pipes, not sure if the brackets would be in the right place.
Then you'd need to modify the wiring loom for three ignition systems.
The engine mounts are different, so would need to move them.
Oil pump must be one for a triple...Basically you'd need all the GT380 running gear.
Wouldn't it just be easier to get a GT380?


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PostPosted: Mon Jul 02, 2018 3:06 am 
Online
To the on ramp

Joined: Fri Aug 11, 2017 7:09 am
Posts: 261
Country: england
Bikes owned: several gt250 ramairs
hi cwilk, i hate to say this and if anybody said it to me i would totally ignore them and do it anyway :D but don't do it! it's not the physical size of the 380 engine, it's the shape. you could fit the 380 bottom end in the 250 frame. easy. but it's the way the barrels point forwards and the cylinder heads even more, they won't fit, unless of course you cut out the 2 front downtubes :D
where would the exhausts run? what about the rear chain run? buy a 380 frame and customise that. usd forks, monoshock it, just don't bother with the 380/250 mixture :D you know it makes sense :D
cheers, dd.

_________________
GTS250 road registered. TS250 engine, Ramair frame.
GT250 big bang road registered. Both pistons fire the same time. USD forks.
GT285 road registered. Overbored - 58mm and TS125 +2 pistons fitted.
GT10 road registered. '65 T10 engine, GT250 frame.


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PostPosted: Mon Jul 02, 2018 2:25 pm 
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Still in the Driveway

Joined: Sun Jul 01, 2018 12:27 pm
Posts: 3
Country: Poland
Bikes owned: Yamaha rd250
Thanks you guys so much for your advice. I got the frame and am starting to do a strip down on the 250 motor. It has good compression, but I'm was just thinking out of the box. My thinking was: 1- there would be more 360 motors and parts to be had
2- always like more power 3- why not :wink:
You guys are the bomb! I was a previous rd250 owner, who never realized at the time how much the bike would be worth (back in the 80's) and bcz I was a total douche-bag and left it uncovered in my yard, it was stolen :oops: live and learn...
I realize now (too many years later) that I like Suzi's better than Yami's and am just starting a life long project, of finally getting 2-stroke smell and sound back in my life :up:
I will keep you all posted on my progress (I know it ain't going to be fast)
Any links to good, inexpensive parts would be appreciated, as I am amassing as many resources as I can!

God-speed!

Wilk


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PostPosted: Tue Jul 03, 2018 1:05 am 
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Expert racer

Joined: Mon Dec 01, 2008 2:52 am
Posts: 1144
Location: Manchester, UK
Which model of GT250 do you have? The 250 motor can easily be tuned to make a useful power boost ...

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1976 GT380 - wounded by me, and sold on
2006 SV650S. It's got cams, and valves, and stuff


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PostPosted: Wed Jul 04, 2018 5:58 am 
Online
To the on ramp

Joined: Fri Aug 11, 2017 7:09 am
Posts: 261
Country: england
Bikes owned: several gt250 ramairs
come on wilk, the more info you give us the easier for us to help you :D the gt250 barrels are really thick and can take a massive rebore. i had a set of mine bored out to 58mm and put a set of flat top ts125 pistons in it to make a gt285 :D she goes like stink. i had a newly rebuilt crank twisted by 180 degrees to make a big bang gt250, both pistons fire at the same time. that thing picks up revs like no other gt250 will. and no, it doesn't vibrate like mad, it's just pure fun. what it would be like if it had a mild tune i don't know. just a couple of ideas. most people over the pond tend to stick a t350 [315cc] top end on, but they seem to be a lot more plentiful in the states than sunny england :D more info off you needed and preferably some photo's.
cheers, dd.

_________________
GTS250 road registered. TS250 engine, Ramair frame.
GT250 big bang road registered. Both pistons fire the same time. USD forks.
GT285 road registered. Overbored - 58mm and TS125 +2 pistons fitted.
GT10 road registered. '65 T10 engine, GT250 frame.


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PostPosted: Thu Jul 05, 2018 5:10 pm 
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Still in the Driveway

Joined: Sun Jul 01, 2018 12:27 pm
Posts: 3
Country: Poland
Bikes owned: Yamaha rd250
Hey dd and gang,
Ok so its a 1974 "Hustler" that was in a spill some time in the 90's. Its got 8900 miles on the odometer (was still connected) and was stored in a shed for about 10 years. The parents dropped it off at the junk yard and I got it for .....are you ready....$250! Its all there, but I want to strip her down and make her a legit cafe 8)

So, I'm living and working here in eastern Europe, and won't be back stateside until next summer. Haven't seen a legit 2-stroke cafe racer in all my years here. So, my plan is to have a buddy strip her down, take the motor off, strip the frame and I am going to start buying parts for her. I will get all my stuff together,confirm it all when I am there next summer, pack the pallet myself (used to be a warehouse shipper) and send it out here renting space in a container. If I try to send the whole bike out still together, I'll get slammed on the access taxes. I'm currently looking at a gt500 that is also in very tough shape, but the 250 is what I will start with and cut my teeth on, until I can step up to something a wee but bigger... :mrgreen:

I'm posting a shot of my sad looking, lonely girl......I can't wait to jump on the beeyach and smell that smell and hear her screaming!
Wilk


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PostPosted: Mon Jul 09, 2018 9:32 pm 
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Around the block

Joined: Tue Jul 03, 2018 4:32 pm
Posts: 78
Country: Usa
Bikes owned: '74 GT250
Thats a nice bike for a cafe project! I'm currently building a '74 Hustler also. I see your gonna need at least a new cylinder head as the one I can see the fins are all busted off. Also try to find the ram air shrouds if you can they help some with cooling. It won't have the low/midrange your RD had being piston port but I think youll like it. Even being piston port they have a nice controllable powerband which is surprising for a 250. I've repaired and rode many old bikes and I think Suzuki did really good with this engine.


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