Scooterotica

8mm packer, RD 400 Conrod, Indian GP 200 webs.

smooth?

Just to help you out, here are the port timings and different stock configurations that can be achieved with a standard totally unmodified GT186 barrel.
Interestingly, you will see that if you increase the rod but not the stroke, the timings reduce. If you increase the stroke but not the rod the timings increase.

A modification for 115 rods is to use a DT175 piston 66-68mm bore and does not require such a thick packing plate. 58 stroke cranks are built without head gaskets while 60 stroke require head gaskets. Hope you find it useful.

58 stroke 107 rod
Transfer 124
Exhaust 173
60 stroke 107 rod
Transfer 127.1
Exhaust 174.6
58 stroke 110 rod & 3mm packer
Transfer 123.2
Exhaust 172.8
60 stroke 110 rod & 3mm packer
Transfer 126.7
Exhaust 174.1
58 stroke 115 rod & 8mm packer (or DT175 piston & 2.5mm packer)
Transfer 122.6
Exhaust 172
60 stroke 115 rod & 8mm packer (or DT175 piston & 2.5mm packer)
Transfer 125.9
Exhaust 173.4

dave wheeler wrote:smooth?

Yes, very smooth. Instant pick up throughout the range, good torque [13 on the dyno], and almost 16hp at 7000 revs [PHBH30 and MB Clubman].

Anyway, ignore those dyno figures, this engine has been a joy to ride over several thousand miles.

I,m building one of these motors using a 110 rod so what if any advantage is there over 107 other than the obvious strength and durability of the yamaha rod?
Looking to make this motor rev on a bit with a jl3 and 28mm phbh also raising the exhaust port by 0.8mm,
If any one can give me any pointers to make the engine quick it would be much appreciated.
Regards

You'll receive lot of private messages from a GT advocate on the forum Nevertheless I just finished my build, rt195 on tv175, long conrod with a special tv rt piston from mb. Super smooth and lovely to ride, although I might have to row gear slightly for best performance around London. Can't comment on GT but build quality was second to none and setup 100% straightforward.


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Rich_T wrote:Just to help you out, here are the port timings and different stock configurations that can be achieved with a standard totally unmodified GT186 barrel.
Interestingly, you will see that if you increase the rod but not the stroke, the timings reduce. If you increase the stroke but not the rod the timings increase.

A modification for 115 rods is to use a DT175 piston 66-68mm bore and does not require such a thick packing plate. 58 stroke cranks are built without head gaskets while 60 stroke require head gaskets. Hope you find it useful.

58 stroke 107 rod
Transfer 124
Exhaust 173
60 stroke 107 rod
Transfer 127.1
Exhaust 174.6
58 stroke 110 rod & 3mm packer
Transfer 123.2
Exhaust 172.8
60 stroke 110 rod & 3mm packer
Transfer 126.7
Exhaust 174.1
58 stroke 115 rod & 8mm packer (or DT175 piston & 2.5mm packer)
Transfer 122.6
Exhaust 172
60 stroke 115 rod & 8mm packer (or DT175 piston & 2.5mm packer)
Transfer 125.9
Exhaust 173.4

Please, could you say what the "deck" is in a standard GT186? Thanks!

I had the James May RT195 kit.
28mm delly bgm clubmand standard cranck. I Was very disappointed with performance.

You won't be disappointed with a GT186. With a good expansion and correct set up you will be looking at performance comparable to non tuned ts1:s on the road. I have tried many different exhausts with it and ended up using a taffy mk4.

I know a few that are not so impressed with the RT195 out of the box. But can be tuned of course.

Gt186 does what it says on the box and then some, I have seen zero bad feedback regarding its performance. There has been discussions about the reeds being brittle but I never had any issues and have extras in my toolbox.

Not happy with my RT kit at all..... enough said