Just wanted to report that I received the two GT5 "type B" 38mm stroke lowers I ordered from thatsdax last week, he was kind enough to add a couple extra parts in the package which was very nice of him to do, the engines look good, I'll have to do some closer comparison to see for sure but it does look as though the transfer passages in the case may be a bit smaller than those in the older GenIV 40mm stroke engines, the casting is a bit rough around edges of transfer areas but nothing that cant be smoothed up easily, the cranks spin a bit tight in both lowers but I've seen the same thing in others and hasn't ever created any issues in my other engines, that tightness goes away quickly after engine is run a few minutes, nothing rough feeling during rotating just a bit tight.
I'm gonna try to get one of these together and on a bike asap so I can honestly report what the balance is like and what I think of the performance that can be expected with just a few basic mods which will be mainly cleaned up ports and I will most likely use a PK80 cylinder that has had the deck shaved to a good height for the Puch 70cc Hi Hi head I plan to use on it.
It is possible that I will just clean up and mod the small port jug just to see what I get from it, but I just don't think good top end speed is gonna be achieved with one of these jugs that have extra small ports in every area.
I may put some very small ramps on piston at transfers if the ports on the jug I use aren't as open at BDC as I would like them to be.
My old Black mountain bike that has the horribly balance old BGF engine on it will be the likely candidate for one of these, it has never seen 40MPH and that is what I will be shooting for, not looking for a 10,000 RPM engine, just something that will be comfortable to ride mid 30's to 40mph when I hit the open road 10-12 miles into town now and then.
Pics below are of the GT5 dax lower, post that will follow this one will be of the jug.
I'm gonna try to get one of these together and on a bike asap so I can honestly report what the balance is like and what I think of the performance that can be expected with just a few basic mods which will be mainly cleaned up ports and I will most likely use a PK80 cylinder that has had the deck shaved to a good height for the Puch 70cc Hi Hi head I plan to use on it.
It is possible that I will just clean up and mod the small port jug just to see what I get from it, but I just don't think good top end speed is gonna be achieved with one of these jugs that have extra small ports in every area.
I may put some very small ramps on piston at transfers if the ports on the jug I use aren't as open at BDC as I would like them to be.
My old Black mountain bike that has the horribly balance old BGF engine on it will be the likely candidate for one of these, it has never seen 40MPH and that is what I will be shooting for, not looking for a 10,000 RPM engine, just something that will be comfortable to ride mid 30's to 40mph when I hit the open road 10-12 miles into town now and then.
Pics below are of the GT5 dax lower, post that will follow this one will be of the jug.
