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My RT225 with 58x107 crank and 17x18 sprockets.The scooter seems to have more compression and it seems hard to kick up.The scooter is at 1.14mm squish.The scooter seems so bad that it takes all my weight (15 stones)on the kickstart,when it starts it seems to run ok.Any help would be gratefully accepted.

Do you mean 18 x 47 sprockets?

Also which gearbox do you have? Some first gear ratios are very high, so you basically try to spin the crank a lot more per kick of the starter lever.

Just taking a quick look and not making corrections for sprocket combinations. The LI125 ratio is 17.38 and TV200 is about 11.

So that means the kickstart lever experiences about 60% more force with the LI125 than the TV box.

I've been a but lazy there and picked the 2 extreme examples, but it illustrates the point nicely.

With respect, as much as any of us would try & help, there are many unknowns that need to be established.

Dickie, (Bless him with his busted leg!) is correct about the transmission & ease of kicking over. However, brilliant though it is that the squish is stated (& a good one for a change) the compression ratio needs to be found out.

I would consider it fundamental to not only your leg but your peace of mind

dickie wrote:Do you mean 18 x 47 sprockets?

Also which gearbox do you have? Some first gear ratios are very high, so you basically try to spin the crank a lot more per kick of the starter lever.

Its a gp 200 gearbox which has the 50 tooth first gear.Your right as usual and the gearbox has 18x47 sprockets.

HxPaul wrote:

dickie wrote:Do you mean 18 x 47 sprockets?

Also which gearbox do you have? Some first gear ratios are very high, so you basically try to spin the crank a lot more per kick of the starter lever.

Its a gp 200 gearbox which has the 50 tooth first gear.Your right as usual and the gearbox has 18x47 sprockets.

Well the gearbox isn't an extreme case. Charging it would help, but not necessarily the best route.

The RT has a fairly low exhaust at around 170 degrees unless it's been tuned?

My RT 230 is reasonably hard to kick over, but not alarmingly so. It has 180 exhaust, longer SX kickstart lever and close ratio box (12:1 vs your 13:1). All of these would.make mine easier to kick than yours. So, I suspect it's just the character of the kit.

As WT1 one says, the compression ratio is obviously key to this but I believe that BGM have sufficiently high QA to make sure that all RT kits have the same head volume.

My RT230 Reed Valve is dead easy to kick over with SX kickstart and Indian GP 200 box with 19/46. I did have a Mugello 230 piston port with same gearing and kickstart which was an absolute pig to kick over. I'm only 11.5 stone though!

Rich'

Take the plug out and connect up a compression pressure guage and report back what the maximum pressure reading is when you kick it over.

Fast n Furious wrote:Take the plug out and connect up a compression pressure guage and report back what the maximum pressure reading is when you kick it over.

I did what you say and the compression was 82psi.

It wouldn't be an s1/2 with a short kickstart peddle would it?

HxPaul wrote:

Fast n Furious wrote:Take the plug out and connect up a compression pressure guage and report back what the maximum pressure reading is when you kick it over.

I did what you say and the compression was 82psi.

That's probably equivalent to around 5.90:1 corrected compression ratio with 170 degrees of exhaust port timing and 5.58:1 with 180 degrees of port timing. Using a GP endplate and GP kickstart pedal wouldn't be the best combination here when trying to get a good swing on the kickstart.
What endplate / kickstart pedal are you using?
Also.... Make sure the chain isn't slack or worn, as this can casue the chain to bunch up and jam between the bottom of the clutch sprocket and the lower chain guide when kickstarting. ( a classic issue with crappy Rolon chains)

Its a series 3,not a gp endplate,with a pulldown GT chain guide with a 82 link iwis chain (not a Rolon chain).As for the kickstart,I use a series 3 engine cover with a gp kickstart pedal.The chain isn't slack at the bottom and I use no bottom guide.

missing lynx wrote:It wouldn't be an s1/2 with a short kickstart peddle would it?

Yes,with a series 3 engine cover and a gp kickstart pedal.

I suppose many owner/self tuners of my generation (very, very late thirties but riding since 1973....) will have always adopted the starting technique of straddling the bike, leant over to the left & full body weight on the kickstart pedal in any case. (Cue Fast Show Swiss Tony)

It seems to my mind the most logical method, & even standardish engines with a fresh bore would require some effort.

Factor in the 70 mm heavier piston with tight clearance to suit the plated bore & you might agree.

Is it easier to start when warmed up?

Well.... the compression pressure is quite high........ so, difficuly in kicking it over is inevitable.