Venlo or bust for Boris build of a true touring-spec Vespa PX?

 

It was too good to be true. As is usually the case where scooters are involved, things didn’t quite go to plan for Boris before leaving for Venlo. If you want to be reminded of (or missed) the first two parts of his BGM 177 kit and tune you can follow these links:

 

BGM kit part one 

BGM kit part two

 

Iggy

Painting the flywheel orange (done by previous owner) is the budget version of a Vespatronic.
Painting the flywheel orange (done by previous owner) is the budget version of a Vespatronic.

Apologies to all of you who expected to read about the preparations BEFORE I headed off to Venlo. But it seems things had been going too smoothly, and eventually Murphy’s Law kicked in.

 

The weak spot in my planning was that the scooter was so far unregistered and with the new engine fitted, it was not road legal, so no proper test riding could be done before taking it to Jockey’s Boxenstop to get the engine spec entered into the scooter’s documents. That meant time would be really tight before setting off, so if any problems might creep up during the last days, I’d be in trouble. But what could actually go wrong? Hmm…

 

But let’s start from the beginning: With the engine and chassis prepared, putting both together was rather easy. Even the SIP Road exhaust went on without any problem – and aftermarket exhausts can really be a pain if you have one of those ill-fitting buggers. The tasks left to do were pre-setting carburation and ignition in order to get the engine running for a start. BGM’s data sheet luckily has quite detailed information on how to set the kit up, so there is little guesswork here.

The channel between float bowl and main jet has been drilled to improve fuel flow
The channel between float bowl and main jet has been drilled to improve fuel flow

SPACO and sparko

 

The carburetor I was going to use was a SPACO SI clone that I had been running in another engine, so I knew it was reliable. I’d already carried out one blueprinting exercise, which I find rather important when using SI carbs on engines exposed to long-distance motorway use. That modification is to increase the size of the small channel between the float bowl and the jets. Usually this is only 1.5mm in diameter, and if you are using a 125 to 130 main jet at full throttle, there is very little safety margin. Drilling the channel to 1.8 or 2.0 mm is commonly recommended and rather easy to do. Apart from that I stuck with BGMs recommendation of 160 air jet, BE3 atomiser and chose a 128 main jet to start with.

 

The other thing is the ignition. BGM recommends 18-19 degrees before TDC, which is just about the original setting. Now any P-range engine has a small cast edge that corresponds with two little notches in the stator plate, one indicating 23 degrees (for the P2) and the other 19 degrees (for the PX). The initial setting here is obvious. However it is common knowledge that these little marks do not always sit where they should do, so the ignition setting should always be checked with a strobe once the engine is running. With an Italian stator-plate in an Indian engine, this seems even more like a good idea.

 

Ignition checked by strobe, 19 degrees are required for the BGM
Ignition checked by strobe, 19 degrees are required for the BGM

Piston slap?

 

With carb and ignition set to their basic configuration the engine actually sprang to life the third kick. A quick spin around the block showed it ran rather healthily and the following strobe check of the ignition revealed that the original markings in my case were actually correct. The only thing that concerned me was that the engine was rather noisy – not only the usual noise of bearings under load and the whirr of the cylinder’s alloy fins, but also an additional pinking rattle – as if the piston was hitting the head very slightly.

 

I checked the squish again, but as expected this was fine. I had already read about some people mentioning piston slap with these kits, and an email exchange with Philipp at SCK confirmed that this was likely to be the issue. Now most Malossi 172 kits for the T5, as well as some others do this from day one without any reason for concern, and with the TÜV date at Jockey’s imminent – plus no opportunity for extended testing, I decided there was little I could do about it at the moment and that hopefully there was no problem anyway.

On the way to Jockey’s
On the way to Jockey’s

Type approval

 

At least delivering the scooter to Jockey’s for the TÜV session worked out without major mishaps – apart from Markus and Jockey giving me a good bollocking for my underperforming front disc brake. I was able to convince them I would look into that again, so eventually they were fine with it.

 

Brits are lucky to have the MoT test – in Germany we must get our scooters through the much tougher TÜV. To explain the TÜV procedure to those of you unfamiliar with German type approval laws: In Germany, a vehicle is street legal only in its original condition. Any alteration of relevant parts like engine, brakes, tyre size etc. must be registered in the vehicle’s documents and this can only be done by a certified TÜV engineer. This is relatively easy with genuine parts (e.g. a complete P200 engine in a PX125 chassis) as the necessary data is officially available from the manufacturer. However if you put together an engine with various tuning bits, the engine spec is a one-off and the necessary data has to be recorded individually, i.e. power output, noise level etc. Plus the engineer has to confirm the rest of the bike is in good condition and able to cope with the additional power.

 

That means, the required preparatory procedures are beyond the scope of an average private person, which is why many specialized scooter shops in Germany offer these services. Jockey’s Boxenstop is a prime destination here. The guys at Jockey’s were positive that everything would go fine, but still the phone call that the PX was ready came as a relief. I finally picked the scooter up the week-end before the rally and was eager to start testing it on the road as the rattling issue was still  wandering around in my mind.

Markus doesn’t like soggy front brakes, or having his picture taken
Markus doesn’t like soggy front brakes, or having his picture taken

Great customer service

 

To cut the story short, I rode the scooter for some 150kms and finally decided that something was not right here. The rattling had got worse, initially it had been rattling under load and at low-to-mid revs only, but now it was there over the whole rev-range and in the end I could really feel it, too. I took the cylinder head and barrel off again, and a look at the piston revealed the problem in all its beauty: the lower front edge of the piston skirt was already visibly worn after this short stretch of test riding. The corresponding rear section at the piston crown showed increased wear as well.

 

Apparently the piston-to-bore-clearance was too big and, together with the BGM’s relatively short piston, this caused the piston to tilt within the bore and wear at an extreme rate. Whatever the reason, no way could I start off with a kit in this condition. By that time it was now late on Tuesday afternoon, with my departure scheduled for Thursday and the engine in pieces again. Great! I rang up SCK to discuss what to do and sent them a few pics of the piston. They agreed that this was not how a piston should look, let alone after such a short time.

 

Now if I have learned one thing in life, it is that it’s relatively easy to be on good terms with someone as long as everything runs smoothly – the real value of people only shows if something goes pear-shaped. SCK really excelled in this situation, with Philipp ringing me back the same evening, saying they were going to send me a new kit via overnight courier the next day, so that it would arrive on Thursday morning. A+++. That would still be a very tight schedule, but at least feasible if nothing else went wrong. Wednesday therefore was rather bizarre, packing up my travel gear without having a scooter to ride – the situation somehow reminded me about the early 1990s, when this sort of last-minute frenzy was common practice. Well, at least I had time to have a look at the brakes again…

Note the worn edge at the bottom of the piston skirt...
Note the worn edge at the bottom of the piston skirt…
…and the opposite side at the piston crown
…and the opposite side at the piston crown

The new kit arrived on Thursday at 11 a.m. By noon I had it ported again to the same spec (sorry I didn’t take pictures again, but I was in a bit of a hurry) and it was up and running by 1 p.m. An extended test ride showed it was much better than the first one – some piston slap still audible, but within normal limits of what you’re used to from other manufacturers. Basically the engine now sounded healthy enough and it seemed to run fine with the jetting unchanged. So I packed my riding gear, saddled up and left home at 4 p.m., swearing to myself about the stupid idea of test riding a brand new kit to a rally 600kms away.

 

I must admit I had not expected the term “test riding to the rally” would turn out to be literally just that.

A 0.1mm feeler gauge slotted between piston and bore
A 0.1mm feeler gauge slotted between piston and bore

 

To follow: The journey to and from Venlo, and the verdict after 1200km’s of hard, fast riding. 

 

Words and photos: Boris Goldberg

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