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I had Superhooper's TS1 in the workshop last night. Nothing serious, but the piston is going to be replaced.

Hooper asked if the scooter could be stroked up from the 58/107 crank that is currently in there, which got me thinking about how people had done this in the past, knowing that the distance from the bottom of the transfer ports to the top of the barrel must be around 58mm.


Roy suggested a 62mm crank. Would anyone like to comment on how they achieved such a conversion?

Knowledge wrote:I had Superhooper's TS1 in the workshop last night. Nothing serious, but the piston is going to be replaced.

Hooper asked if the scooter could be stroked up from the 58/107 crank that is currently in there, which got me thinking about how people had done this in the past, knowing that the distance from the bottom of the transfer ports to the top of the barrel must be around 58mm.


Roy suggested a 62mm crank. Would anyone like to comment on how they achieved such a conversion?

I currently run x2 TS1 with 60x110 cranks
Ones on Indian casings using a 2.5mm packer & thick head gasket
& the others same but on Spanish casings & mammoth head fitted ..
I Love em.... Torquey & both run quite Tall FD gearing 4.4 & 4.6
Iv messed about with a few diff pipes on them too

Tell him to go for it
We’d all love a diff ride

So Norrie, you were able to accommodate the extra 1mm at TDC and BDC with a thicker head gasket and a base plate? No recessed head or similar?

Hi there, if your looking at A 62mm stroke there is quite considerable work to get it right as the port timings/Duration will be altered considerably, there are a lot of stroked motors out there running fine, however they are not the best they could be, ideally the cylinder base should be machined and the cylinder lengthened to get the port heights/Timing to a reasonable level
also there would ideally need to be a channel machined in the crank-case to accommodate the rod/big end as it will often protrude from the circumference of the crank web and hit the casing, if i can find it I'll post up a dyno print out were there was considerable improvement just by correctly fitting the cylinder to a stroked motor a before and after reading.

Knowledge wrote:So Norrie, you were able to accommodate the extra 1mm at TDC and BDC with a thicker head gasket and a base plate? No recessed head or similar?

Hi Martin

I run a 60mm x 110mm crank in my TS1 with a 3mm packer and no head gasket.

The 60mm crank was put in without actually realizing it was 60mm, but if I'm more than happy with it and it does feel as though it pulls a bit better than when it was running on a 57mm x 110mm crank.

Toot

Hi Martin,
60x110 crank also used here on my ts1 with no trenching to the casing using 3mm packer and 3 bond on the head certainly pulls better.

Bare in mind that not all 62mm cranks need 'trenching' as such, the Grand Tourisimo 110/62 needs little more than dremelling

I have a 253 cc TS1 64 x 71

The crankcase needed machining to take the larger stroke.

The barrel had 5mm of weld added to the top before machining and re-plating to keep the port timings sensible.

The rod length is 116mm with an 18mm pin. The piston is a Wiseco IT250 71mm.

Knowledge wrote:So Norrie, you were able to accommodate the extra 1mm at TDC and BDC with a thicker head gasket and a base plate? No recessed head or similar?

No recessed heads mate
2.5mm base packer & whatever head gasket I needed to give mine a 1.2 - 1.5mm squish clearance

Some 60x110 cranks you may need to trough out the crankcase a tad

GL

Thanks all.

I am not surprised by your replies, which were all helpful. I think a 60mm stroke is the sensible limit without having to consider significant changes to allow for the traditional (58mm stroke) ports.


Thanks again