Indian GP Build Part 11

Dry Building

Someone on Facebook mentioned how we just used to build and ride scooters back in the Eighties. Yep, we did. And some were quick, some were slow, some ran forever, some constantly blew up. Personally, I wouldn't have known a squish from a pumpkin and jetting was guessed. I did set timing, using Rizla papers and trusting the existing marks...We now have access to decent manuals (thanks Sticky) and the two-edged tool below.

Anyway, it's time to dry-build the top-end...I'm fitting a CASA Blackline  piston and head in place of the worn original piston and standard 225 head. The head is a nice bit of kit. It uses two dowels on two of the engine studs to solve the problem of the standard head possibly fitting in a slightly different positions each time the top-end is built. It's also thicker which should make it less prone to warping. Fitting the dowels requires drilling down two of the barrel stud holes to a depth of 5mm or so. Easy job, but lacking in bench space I first have to set up the bench drill. This takes longer than the actual drilling. The final fit is nice and snug. Yep, I'm going to harp on again about a simple solution to an old problem...

The Blackline piston is made by Meteor. Interestingly I remember these as a mid-range piston back in the eighties/nineties. Certainly not as good as an Asso or Jap one. How times change, Italy now being a supplier of quality rather than cheaper stuff...It uses the C circlips, which are good but a bastard to fit. Fortunately Casa came up with a tool to sell us that solves that problem. Erm, anyway, they do fit very tightly and should stay where they belong.

Small-end bearing lubed and piston fitted...The Jasil crank came with a quality small-end bearing, but this got pressed in to service as an emergency replacement for the one in Nicky's S1. Anyway, Steve supplied a decent quality one...

A quick check shows that the TDC is still good. It shouldn't have changed in theory but no harm in checking.

The next job is to check the squish clearance, which needs to be between 1mm and 1.5mmm. When doing a dry build the most accurate measurement is achieved by fixing some solder to the piston in two V shapes, in parallel to the gudgeon pin. Hold these on with some grease, torque down the head to 15 foot pounds and turn it over TDC. It'll be stiff at the top as it squashes the solder. Take the head off and measure the squashed bits with a Vernier gauge. A bit of a pain but definitely better than putting a single piece of solder down the spark-plug hole, which will probably give a higher reading (the piston being squashed to one side...). I'd always used the latter until reading about the former in Sticky's manual, which made more sense in my head. I'd still use the solder down the plug technique in preference to stripping a built top-end, but might be a bit concerned with a 1.1mm result...

I get a smallest measurement of 0.93mm and largest of 1.05mm. Dammit too small! I could possibly get away with this, but possibly getting away kind of defeats the point of a dry-build. I could fit a head gasket or use a fatter base gasket. I don't have a head gasket (and would probably struggle to get one thin enough) and prefer not to fit one with the Casa head. A hunt amongst my gaskets reveals a fat one, which I'm going to try. Unused it is 0.4mm thicker than the one that has been torqued down. I'm guessing this will mean 0.2mm to 0.3mm when fitted, which should be sweet. It needs trimming to match the larger TS1 transfers...

A fatter base gasket will move the barrel up relative to the piston and slightly move the exhaust/transfer port openings, but 0.2mm shouldn't matter. I'll check though...

Looking at the top of the TS1 barrel I can see that someone has tightened the head down so hard at some point that the head gasket has left a dint in the aluminium barrel! I want a perfect seal. Normal advice is to lap the head on some wet and dry taped to a piece of glass. Great assuming your barrel is flat, which is probably true with an iron barrel. I decide to lap the head and barrel together using grinding paste to match both parts. I used to do this all the time and chatting with others it seems I'm not the only one.

A sign of a good seal is when the paste sticks the head to the barrel 

The next job. Fit a TTO cylinder head temperature pick-up. Most Lambretta heads need some Dremel work to allow a TTO CHT gauge to be fitted. The Casa one is about the easiest I've ever done, just requiring a small bridge of metal to be removed. 

Next. I'm using a YPVS reed block, which requires a packing plate. These plates are manufactured specifically for this job, so you'd think they would be a perfect fit. Yeah, nah, a bit of filing is required.

The final job is to check the fit of the MB flange type TS1 manifold. This is a perfect fit. I'm replacing the mammoth 34mm carb with a more sensible 30mm one, hence the new manifold. It looks lovely as well!

I've gone about as far as I can with the top-end until the bits I've ordered from Steve arrive...so I turn my attention to the chaincase cover. The Indian kickstart bushes were very badly fitted.

Possibly not a problem for a standard motor, but the AF 5-speed box needs 1.5mm more clearance than a four speed, and that's over 1mm used right there...New Scootopia bushes are fitted simply by heating, tapping out, tapping in etc. 

The kickstart ramp holes are cleaned up with a tap, the bushes lubed with grease, the kickstart oil-seal is fitted,  and then the kickstart shaft.

The AF 5-speed instructions emphasis the importance of making sure the kickstart shaft is held as far in as possible, to maximise clearance to the new box. They say at least two shims are usually required. I fit 2 standard ones and a thin one to give a nice tight fit. Fitting a Readspeed style circlip with extra tabs, as advised by Sticky, is a must! Steve carries these in stock at Lambretta Obsessions.

At this point some complicated clearance checks are required in the AF instructions, and I'm buggered, so time to call it a day.

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