Engine Build - Advice needed

[Richjak]

So I am just about to start building a fast road engine for my cut down Vespa based around P200 engine casings and have more or less decided on the following spec and have spoken to SIP and a couple of mates about the build, all of them have various ideas on how well it will perform and what they would do different to improve the performance. At the moment I have the casings and the cylinder, and expect to take delivery of the reed valve soon. With these parts I will be able to start the porting work on the casings. The rest of the parts are not ordered yet so could be changed if necessary. The scooter will be mainly used for fast road use on the local bypass and not for blasting down the motorway for hours on end.

Engine Spec:

Malossi 210 kit (MHR) with MMW head, Polini 60mm balanced and gas flowed 60mm crank, Cosa "sports" clutch from SIP, 23/64 Malossi gearbox. Carb is a 28mm Delorto on a Malossi intake manifold (already have this) mated to a ScootRS Atomic "mini" reed valve. Ignition will be Malossi Vespower system with an MMW lightened flywheel and the exhaust will be the SSC Polini RHS replica (more for the looks).

I know from reading the other posts there are some very knowledgeable people on the forum that will be able to see things that I have perhaps over looked in this engine specification or they might perhaps do differently and would like to get some feedback on my choice of parts and what sort of power I can expect. Please note that this isn't my daily runner so fuel economy isn't an issue. The scooter is presently running a 177 Polini kit, with the pro series balanced crank, 23/64 gearbox and 28mm carb and SSC Polini pipe. I am quite happy with the performance but (as usual) want more. The spec above, as I see it, is a step up based on the engine set up that I presently have.

Thanks in advance.

[GLscoot]

I would consider changing the reeds, I'm not saying scootrs products are not very good but with the money you are spending I would look at the RD350 reeds. The actual reed petals are known to shatter, so buy the best you can.
gaz powell is building a very similar spec engine and has shown some excellent pictures of the work done so far. I will be picking his brains shortly on some of the stuff he has done.
What sort of speed were you getting from your original set up.
I don't know anything about the Malossi ignition system, but I can recommend the Pinasco Flytech. What ever you decide check out ebay.it first for the system. Even with postage it works out a lot cheaper than SIP and certainly cheaper than VE UK.
Heres the link for the pinasco flytech, and the malossi
http://www.ebay.co.uk/itm/351046308372? ... EBIDX%3AIT
http://www.ebay.it/itm/5515702-ACCENSIO ... em5b02bee2
gary

[ipman]

keep the 125 engine and swap the polini for a parmakit 187cc,,reeded and ported would pi55 all over a 210cc

[Juan]

If you must use a Cosa clutch then make sure the basket is banded and the turrets are 22mm deep. I'd also get a shorter 4 cog in it.

[Jack221]

A 23/64 cruiser gearbox is going to go ok but will never really make a proper quick scooter. Even the standard 23/65 is already too high, for fast road. If looking for high speed is is best to reduce the gearing to 21/65 and port it to aim for 9000 rpm in top (which is about 88mph on GPS and safe piston limit on 60mm). I think that anything over GPS 85mph on a PX is scary enough for anyone. And if you must have reeds, then the RD350 are the best for the job with a 34mm Delly carb.
Good luck with the build

[Richjak]

Thanks guys this is exactly the sort of feedback and comparisons I was looking for

[Richjak]

I would consider changing the reeds, I'm not saying scootrs products are not very good but with the money you are spending I would look at the RD350 reeds. The actual reed petals are known to shatter, so buy the best you can.
gaz powell is building a very similar spec engine and has shown some excellent pictures of the work done so far. I will be picking his brains shortly on some of the stuff he has done.
What sort of speed were you getting from your original set up.

Thanks Gary - will look at the 350 reed valve and give it some consideration as my reed valve hasn't been delivered yet so maybe I can upgrade it and pay off the difference. I will also have a look at Gaz Powells thread.

The original set up is good for about 70+ but with a blistering acceleration through 2nd and 3rd but then chugs off in 4th due to the gap on the Polini gearbox. The plan is to use the carb and gearbox from this engine for the 210 lump and fit this engine with a standard 24 mm carb and P200 23/65 gearbox as I am planning to fit this engine into my full bodied sprint which I use as a daily runner and hope that these modifications to the spec will see better "behavior" from the engine.

[Richjak]

keep the 125 engine and swap the polini for a parmakit 187cc,,reeded and ported would pi55 all over a 210cc

To late now mate I have already got the 210 kit. Useful advice though as I will still keep the 150 engine.

[Richjak]

If you must use a Cosa clutch then make sure the basket is banded and the turrets are 22mm deep. I'd also get a shorter 4 cog in it.

Yes indeed I was planning on getting the Cosa II sports clutch which has been banded by SIP, good advice about the cog as I hadn't considered that.

[Richjak]

A 23/64 cruiser gearbox is going to go ok but will never really make a proper quick scooter. Even the standard 23/65 is already too high, for fast road. If looking for high speed is is best to reduce the gearing to 21/65 and port it to aim for 9000 rpm in top (which is about 88mph on GPS and safe piston limit on 60mm). I think that anything over GPS 85mph on a PX is scary enough for anyone. And if you must have reeds, then the RD350 are the best for the job with a 34mm Delly carb.
Good luck with the build

Thanks for the info about the gearbox - I am going to stick with the 23/64 as I already have it in the 177 lump and feel that the extra cc of the 210/60mm set up will over come the issue of the gap between 3rd and 4th gears. Just out of interest what has a 21 tooth cog in the gearbox ?? As for 88MPH that would be terrifying where I live which has a 4 lane Bypass running around the coast and in a few other areas but the majority of the Island is nothing more than country lanes.