GT186 with Li Crank

[Hughieboy]

Hi,

I'm thinking of adding a GT186 kit to my S3 Lis engine (fitted to an S2)

Spec is currently;

Harry Barlow built motor by obvious owner
30mm Dellorto PHBH
TSR Evo Pipe
Pacemaker gears
Varitronic ignition.
HB rebuilt crank with 117mm (I think) MMC conrod
There is a base packer.

It had a 22mm Jetex and a Clubman pope when I first bought it, performance is now better but not great.

Standard advice seems too be to junk the Li crank and fit a GP one.

However, as the engine was built by Harry he must have had a reason for using the Li tapered crank and as the engine has been professionally built and has done fairly low miles I'm loathed to start replacing parts unless it's necessary. I'm assuming Harry would have taken into account that the engine was going to be more powerful than standard after he'd finished with it and wouldn't have fitted what's in it if it wasn't up to the job - it would have been a straightforward thing to do to replace the crank with a GP one when it was being built if he had thought it needed it, the previous owner told me it was an expensive build so I'm sure he wouldn't have skimped on something so important.

I'm not an expert, would he have used a stronger than standard crank that happened to have an Li taper if there is such a thing? It's just that if I change that I then also need to change the Varitronic flywheel and I'm trying to keep a lid on costs if possible.

I want to do this as it is a good reliable motor but but it just isn't very quick, top end balls out would be in the region of 60mph GPS, cruising at around 50mph. As the Varitronic flywheel is quite lightweight so presumably there will be less stress than with a standard one, I'm tempted to try it but wondered if anyone has any sage advice on whether I'm asking for trouble?

Would be grateful for any voices of experience, either with the what/why on Harry's cranks or whether it's just a no-no and I'm taking unnecessary risks with the rest of it if I go ahead. I'm not looking for TS1 performance but need more than I have.

Any solid advice appreciated, thanks...

[Hughieboy]

** Previoius owner, not obvious owner ...

[dscscotty]

My own view would be to change to a GP crankshaft, any significant increase in BHP will also increase the chance of the taper failing, I've seen several snap over the years and the damage can be quite severe in that it often takes out the stator plate and or mag housing, also modern GP crankshafts are fitted with a 22mm diameter pin which means that more modern or Japanese performance big end bearings can be used, There is also a wider option conrod wise, there are some decently priced mid range crankshafts available that would be upto the job!

Good Luck!

[bsso78]

As already said above.
I also happen to know that the bloke above can put together a decent crank that would be perfect for your needs, drop him a pm and he’ll sort you out!

[Covboy]

I had a 186 making about 15 HP on a LI crank, standard li150 gearing, variatronic - no issues over 4000 miles....

[martyn dwane]

"It had a 22mm Jetex and a Clubman pipe when I first bought it"

perhaps when harry built the crank, it was for the a standard barrell ( maybe ported ) with a 22mm and clubman, as you state in your post.

[Hughieboy]

Thanks guys, that corroborates with everything I’ve been told and I take it all on board.
Having said that, I’m encouraged by what you said Covboy. The scooter is unlikely to do high miles.
I’ll do some sums and make a decision,
Cheers for the knowledge all

[burnside]

Crank aside, what gearing are you running? My GT186, PHBH30 and Fran Race will cruise comfortably at 60-65mph with plenty left for over-taking.

Also interesting that you've got Variatronic ignition, Rich Taylor advises against those with GT kits but I can't remember why. He does recommend changing to a GP crank and electronic ignition timed to 19 BTDC with clubman pipes and 17 BTDC with expansions

[Hughieboy]

I have Pacemaker gears but I’m not sure in the actual sprocket sizes. I’m planning on stripping it down a bit over the weekend hopefully so I will have more info on the internals.

I bought the Varitronic when my old Indian 12v system failed, to be honest I was feeling flush at the time and was a victim of Cam Lams website speil, I have since read that I could have bought something more versatile (and probably less expensive!)

I haven’t had any problems with it but equally I’m not sure what the benefit has been either, it starts, stops and goes - just like it did with the old set up!

[Covboy]

Re Variatronic

I have run these on all of my scooters without issue, Ive not had a ever had any CDI or Stator problems in about 5 years of using them - fit and forget....
The only issue I have is the relatively low power output meaning a dimmer headlight at lower revs.

[Hughieboy]

Re Variatronic

I have run these on all of my scooters without issue, Ive not had a ever had any CDI or Stator problems in about 5 years of using them - fit and forget....
The only issue I have is the relatively low power output meaning a dimmer headlight at lower revs.

Yes, it is problem free. I’m just not tech eniugh to realise the full benefits probably but it does start easier and probably revs more freely if I think about it.

What kind of real world performance are you getting from your GT kit? Decent acceleration and cruising speed without wringing the knackers off it?

[Covboy]

13 stone , riding solo comfortable at 55 - 60 mph - not squeezed much more out of it (Af clubman.)
About 11 miles per litre. I’m a fan of the gt kits

[dickie]

Crank aside, what gearing are you running? My GT186, PHBH30 and Fran Race will cruise comfortably at 60-65mph with plenty left for over-taking.

Also interesting that you've got Variatronic ignition, Rich Taylor advises against those with GT kits but I can't remember why. He does recommend changing to a GP crank and electronic ignition timed to 19 BTDC with clubman pipes and 17 BTDC with expansions

I was advised to chage my gt186 ignition from varitronic to fixed electronic at 18degrees when I was looking for better performance; made no difference. It's also alleged to be the cause of broken reeds but there are more compelling arguments put forward by Darrell Taylor.

[dickie]

13 stone , riding solo comfortable at 55 - 60 mph - not squeezed much more out of it (Af clubman.)
About 11 miles per litre. I’m a fan of the gt kits

I initially ran mine with ancillotti 42mm clubman and 25mm phbl. Got just under 10bhp but nice to ride.

Changed to 30mm phbh and a bgm clubman and got more like 14bhp but just as nice. Also, I overgeared at 4.7 to begin with. MUCH better at 5.1

[Hughieboy]

I’ll need to look at gearing, the current set up seems a bit short in the leg.
Haven’t done that before, i’ll need to ge the casing off so I can get an understanding of what I have specifically then alter as necessary...