LCGB Forums

First of all, a big thanks to Weeksy and all concerned for getting us back on line.

Anyway, this is my Davos ride last weekend:







Engine is a standard GT186 albeit with a RD400 115 conrod, MB Clubman, 30mm PHBH, 4.9 fourth drive ratio. It used to be in my cutdown. It runs really well. It was on the dyno about 18 months ago and, from memory was 16 or 17 bhp and plenty of torque. I love it

That said, tomorrow the engine gets dropped again. The gear change is too stiff and given that my round trip is touching 2000 miles, I need to try one last time to sort it. It's over 2 years since I built this engine. Rather bizarrely, I woke with a start early one morning this week with that Eureka moment when I think I know what it is

I'll let you know in due course whether I was right LOL

You taking the old landrover as your back up van G.
Nice combo.

Mr G in NYC wrote:You taking the old landrover as your back up van G.
Nice combo.

I parked up next to it only so I could show off my better paint job, Grahame

Good to see all the members beginning to drift back. Thank you to all the LCGB people who've got us back on line. Paul, my money's on the stronger kickstart plunger spring in the sliding dog ???

I see what you mean about getting them engine cones in that toolbox

Looks well Paul

Indeed, mate. I'm a one man back up van for Davos

Well I sorted the issues with my stiff gear change today It was either the gear selector spring or the sliding dog itself. The old spring was virtually the same size as the new one I bought and was not noticeably firmer, but I did notice that the new one had 12 winds, the old one 13.

In previous engine builds, I've either re-used the original sliding dog, or bought good quality Italian ones. On this build I fitted a SIL one, having read that they were good. I do remember not being too impressed with it when I fitted it but thought "it'll be alright."

Anyway, today I compared it to a new MEC/EUR one. Essentially the Italian one is well finished with nice chamfers to the edges. If you run your finger over the track that the ball bearing follows the ridges are smooth. The SIL one I had fitted was anything but. Next to no chamfers and the path that the bearings had to follow had sharp edges. I'm inclined to think that the main issue was the sliding dog and not necessarily the spring but who knows. It works

Love the scooter Paul but that leggie toolbox is sumat else, lol. Love it though.

Rich'

At first glance, thought someone had s**t on your seat in the third image, but quickly realised it was the top of a post behind the scoot

Nice images.

Well the GT186 completed the 1800 round trip in almost fine fettle. Lost a panel handle in Germany on the way there and the tailpipe on the motorway near Metz. Oh and my kickstart mount is on it's way out too.

Engine was revving between 5500 and 7000 for most of the way back from Harwich yesterday fully laden. The noise from the MB clubman without a tailpipe was absolutely glorious

If the lady with the small child in Breda is reading, I do apologise for scaring your boy with the noise.

just luvin' that box, and i thought i had a big one

Storkfoot wrote:....Oh and my kickstart mount is on it's way out too..

I don't know about 'on it's way out, your scoot was the only one I followed that left 2 tracks in the rain

Very impressed with the performance of your GT186 lump though especially as you carried all your gear for much of the ride

Cheers, Col. You must be right about the mounts. I shall be ordering a new set in the next few days.

As for the GT, well suffice to say I left the TS1 at home. If anyone wants testimony as to how good the GT186 is feel free to PM me.

I only dropped the engine to fit new engine mounts but then thought I'd give it a once over. Engine has now done about 4500 miles from new.

The crank is Indian GP200 webs with an RD400 conrod. No thrust washers. Big end bearing all still looks good as does conrod and webs.

Top end __ no evidence of any leaks at all but a bit of blow by beyond the rings. There was no feathering of the reeds, however, they had bent back a bit from the top of the cage. I decided, therefore, to treat the engine to new rings and reeds:



Anyone know why the top ring on RD pistons is thinner than the bottom?

Do I win the prize for the spring in the sliding dog ?. You've got me a little worried now Paul, I've just rebuilt an engine with a sliding dog of unknown origin. I haven't fitted it to the scooter yet, but if it turns out to be a dud, it's an awful lot of work to replace it as you know.

Geoff, I have kept the SIL sliding dog as with a bit of patience I suspect you could dress it to be perfectly functional. I'm just happy that I sorted it before Davos as the trip there and back with the gear change as it was would have almost ruined the ride.

Clubman now properly repaired by MB. New engine mounts too, oh and a CamLam breath sweet filter. Front brake now working well, however, this has exposed that the front suspension is not up to it IMO.

Storkfoot wrote:Anyone know why the top ring on RD pistons is thinner than the bottom?

Paul,

I think the top ring is not just thinner, but a different shape. I think the top ring is tapered, while the bottom ring had parallel top and bottom faces. Not only do you have to fit the right ring in the right groove, you need to ensure they are the correct way up.

Why? The theory is that as the tapered ring meets the pressure of the combustion process, the pressure forces the ring tight up against the wall of the cylinder.

My guess is it transfers less heat to the barrel wall having a smaller contact patch, the top ring holds most of the heat back from the combustion process in sealing the bore. plus it should be more flexible being thinner and can more easily flex better over an open un-bridged exhaust port and as the top ring holds most of the combustion pressure's I would also guess it offers less drag.
The heat and pressures are more diluted by the time they get to the lower and thicker piston ring.

I'm only guessing so there is no real concrete fact behind this guess.

Thanks for that, lads. Martin, from memory there was no discernible difference in the rings other than the width.

Paul,

I could be mixing my pistons, and I might be confused between the TS185 piston, and the RD350. It have both pistons, but I can't find the. RD item at the moment.

I might report back if I can find it.

Martin