I really enjoy moped racing. I went to the last race of the first Polini Cup in 2009, started a moped racing circuit in the pacific northwest in 2010 that ran for a handful of years, attended Tomahawk Cup, the first 3 Moped GP West, and other various smaller events. Now that I’m back in the midwest it’s a given I’m going to Moped GP Midwest. With the dates being September 11-12th I don’t have much time to prepare. Well, honestly, I never have a running bike until the night before I have to leave to attend the race so I’d like to do a little better than that this year. Also honestly, I start more projects than I should and then panic while working until the last minute. My projects this year are two new hobbit motor/ drivetrains of which I will get into the details of soon, and a stock class Tomos A55 ST Classic. My stupid brain is more excited about the Tomos so we gonna talk about that first.
Moped GP’s is not so much a cohesive organization with common rules and regulations and more like a umbrella term for moped racing. But they still just use the loose class definitions off the website, so lets look at that:
Ok, well, there isn’t much to go on here so I guess I will try to interpret this as best as I can. Frame says “stock” while other classes say “modified frame”. So I assume here I must use a moped frame, but I cannot change anything on it. That sounds like less work for me then so lets run with that. Bottom end says stock, so engine cases must be stock. Now it does not say what I can do to modify them though. Is welding allowed, what about machining, basic porting and case matching? Well it’s not clear so I’ll assume I can if I want. Top end says 50cc max. Ok now that’s too vague, because I can by some quite serious 50cc top ends for a moby, but again, I think it’s implied it must be a stock cylinder as it would have come on a moped. Trans must be stock too, but how much? Can I use clutch springs, after market clutches, variator parts, weights, 3 shoe? Hmm.. I wish these had better defined rules, but I doubt they would disqualify you for a polini variator on your ciao, or maybe they would. Carb says 15mm max, but does not say it has to be a stock moped carb. That does give you some interesting options like a basic Bing 15 or a PHBG 15 too. Exhaust is just open which is nice and easy to interpret.
Now let’s me explain how I plan to interpret these rules. I think a stock class moped should be a moped sold in America with pedals. So no Derbi Revolutions, AV10 moby’s, Peugeot SPX’s, ect. I will assume stock frame means no major modifications but minor ones would be allowed. I mean things like changing seat mounts, removing extra brackets, trim fenders, would be allowed, but not welded cross bars or top tanking a step through frame. Engine cases I feel implies I am allowed to do removal modifications but not additive mods, so I can case match or open reed block openings but I can’t weld new case induction reed block onto E50 cases. For the transmission I think major parts must be stock as sold in the US but you can change tuning parts. For example you can cut windows into the stock hobbit variator but you cannot run the Camino 6 roller, and no TJT aftermarket variators. I would allow an aftermarket e50 3 shoe because they were stock here but not a Treats clutch. Also you have to be able to change gearing. Be ridiculous if you couldn’t. Top end I feel I’m allowed to port it in whatever way I can figure out how to do. Same with machining. I would also say you have to use the top end that engine came with, no top end swapping. No A35 top end on a ZA bottom end. It should be the same brand top to bottom. Carb and pipe is pretty strait forward but suspension, brakes, tires, and other odd stuff isn’t really addressed. It doesn’t say I can’t use alcohol as my fuel or even high octane race gas so I guess those are option. Slicks too if I can find them. I guess, my point here is the rules are generally vague and a clever person could get real wild here with stuff that’s not really in the spirit of stock class but not expressly forbid.
I have at my disposal a fairly fresh Tomos A55 classic, and for my money, I think it might be one of the best options available for this class. Everything on it is just so nice and new, and works so much better than the old bikes. It has 30mm hydraulic forks with very good brakes front and rear. The carb is a 14.5mm Dellorto PHVA that uses the full complement of adjustability. The top end has 4 transfer ports, simple round intake and single oval exhaust that stock will rev to 9k rpms, with lots of heat fins, and a very good designed head with an actual combustion chamber. The 2 speed transmission is easy to tune and the clutches are not hard to tune either. The stock ignition is a very reliable and strong cdi as well. It’s a very solid starting package for this endeavor. One that I think could make a lot of power with not a lot of modifications. It also helps I’ve spent a lot of effort over the last year tuning my daily Tomos so I’ve got a very good idea of how to attack this problem. Depending on how stock all the other bikes actually are I think there might not be much better options out there actually. Next time I’ll get into the teardown and the details of plan but this will explain the basic overview. I’m already excited about it.