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250 2C racer project

12K views 21 replies 6 participants last post by  smokey125 
#1 ·
Hi I’m new on the forum and I have some questions about the 250 2C.
Thought I would start with an introduction to myself. I started riding schoolboy trials 24 years ago and I’ve been racing bikes for 20 years I’ve always ridden classics and for quite a few years modern bikes as well.
With the ever tightening budgets I’ve decided to go a slightly different way and I’ve just brought a 2C (it’s actually a Moto Guzzi TS but I prefer the Benelli colours) to race in the BEARS class at BHR and the air-cooled post classic class at CRMC.
I’m doing this on a budget so upgrades have to be as cheap as possible!!! I know the bike won’t be quick at first but I can develop it. I have several friends that are very good with two-strokes. If nothing else it will go round corners well, at BHR circuits this year that could be enough.
The bike has a Grimeca drum front brake which I am planning on upgrading to disc. So my first question is, are the sliders interchangeable between the two different forks. I’ve seen second hand sliders (354 and later disc 2C’s) fairly cheap can I swap them over?
Other than that the only question I have is does anybody know of a colour code that is close to the old military green they used on the 60’s race bikes? I would love to finish it off in green and silver.
 
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#2 ·
The later 2 c have different yokes as they have Guzzi type forks instead of marzochi. i believe the guzzi v50 has the same forks as a 250 2c they also have 2 caliper mounts. The later 2 c has an alloy barrel and larger carburrettors is said to be 32 bhp instead of 26 bhp on the earlier model.
The bike itself is only 231cc there was a kit to bore the iron barrell out to 250cc but i am not sure what pistons they used. The Benelli motobi club know some people who have tuned and raced some 2 c.
I loved both the 2 c i had in the past great 2 strokes !
 
#3 ·
Ok that's lots for me to go and have a look at tomorrow!!!
I've seen a pair of V50 sliders for £50 so that could be a good start point and change just the one side. I've found the forks a bit confusing they are Marzocchi's but are completely different to the ones fitted to Ducati's of the same period but the breaks are the same.
I'd not read anywhere before that they changed the barrells from iron to ali, from an inital look the other day I thought they looked like ali. I was hoping they would be ali nikasil plated as the bore and stroke are 56x47 it's already short stroke the last thing I would want to do is bore it any bigger the TZ's were 56x50 up until the mid 90's before they went the same was as everybody else and went to a 54x54. The longer term tuning plan was to modify/make new crank get the stroke out to 50mm end us TZ, YZ or RM 125 pistons to get the full 250cc capicity. Short term it was going to be carbs, heads, mild porting, pipes and ignition.
 
#5 ·
Hi Smokey, I can put you in touch with John South, who is based on the IOM and has extensive experience in using the 2C for racing. If you are going to race it then apparently the right side of the frame, near the bottom engine mounting bolt needs strengthening.

I have a 2c myself and planned to do the same but I am enjoying MZ racing and realistically am never going to get round to converting my 2C.

Chris G from this forum gave me a frame, some pistons and some spare heads / barrels (one of which I believe is nikasil lined). As I am not going to get round to using them, you are welcome to them. The only thing I ask is that you use them or keep to offer someone else on the forum.

I also have some racing yokes and some clip ons somewhere but will probably ask for some money for those.

Let me know if any of this is useful to you.

Cheers,
Lee.
 
#6 ·
That would be great on all counts, especially any frame mode like that. A quick look at the frame and I thought it would be pretty bomb proof! Starting with a bare frame would be great as well, as I can compare it with a built up bike as you go helps a lot in my experience.
 
#8 ·
Interesting topic, as I have just come into a 2C and would be interested in getting any useful information on preping a 2C racer. Chassis seems pretty straight forward, but engine prep needs a little more thought I would guess:

- I see from a general web trawl that some folks are running 250s. Any idea how this is done? I would imagine it's a stroked crank? Any idea who does this sort of stuff?

- Could someone advise on the 2C gear ratios or better still how you might close the ratios up a little as I assume for road use there was a pretty mide spread?

Finally has anybody got any 2C engine spares they may want to part with

Thanks for reading
 
#10 ·
To be honest wezzo it depends on how much you can do yourself, who you know who can help and what your expectations are.

I'm setting myself up for problems from the start by trying to build mine to both BEARS regs and CRMC post classic air cooled regs!

Personally I chose a 2C because I love two strokes, there a little bit different and when you look at the circuits BHR are going to this year a sweet handling lightweight bike should do well.
I also think the engine has a lot of potential but I know a lot of guys who are very good at making two strokes go very fast.

Don't be fooled into thinking that the cycle parts are that easy. If you have the drum braked bike it will do to start but isn't up to hard racing. From all accounts the standard rims can be a bit weak so probably need changing.

Don't let any of this put you off. BHR is great fun to race with and not too serious! I think a carefully put together set of cycle parts and an engine with mild state of tune would be plenty of fun and not be last.
I'll pm you more information tomorrow.
 
#14 ·
Funny you mention the Dellortos. I have a set of 30mm Dellortos from a Moto Guzzi Lario. Obviously 4 stroke, so not entirely sure they would work on a 2t. If its a jetting job I wouldn't really know where to start. So I guess the question is 'what jets would suit these Dellortos?
 
#15 ·
Don't see why you can't change them I don't think the bodies are different but I'm sure the guys at Dellorto uk could advise they were really helpful when I needed some bits for my trials bike carb.
It's Dellorto or Amal I can't help but feel the Amal's are a bit crude! Run them on the classic Ducati because the Dellorto's are too new.
 
#16 ·
Out of interest what are your aims, what sort of racing experience do you have, what do you hope to achieve?
For me this is an exercise in enjoying racing without getting too silly on costs. I'll be racing my dads Ducti again this year. We have developed this continuously over the last 18 years to make it competitive, in terms of hours put into it it has cost a fortune. It has a 6 speed gearbox that we designed, our own bodywork, modified clutch from a modern bike, half the ignition system was made in house. My dad and I are both engineers, my dads been involved in racing since the 60's. The result has been two CRMC championships a 3rd place at the MGP as well as a good selection of other top 10 finishes, but its been hard work and the budgets are getting bigger and bigger at the front of the CRMC and we can't go on much longer.
I could easily go the same way with this but don't want to, that's why I've chosen this bike in the BEARs class.
 
#17 ·
Hi. I venture out with CRMC when I can, but am constrained with time. mainly due to work. With this bike I'd like to make a half competant racer but without too much expense. However I always say that and end up bulding a minter that costs a packet.

The plan is to uprate the suspension, add some bracing in some places, start with a drum but probably go front disc (anyone know for a 2C front wheel?)

Engine will be tuned and taken to 248cc with bigger carbs, chambers and electronic ignition. I've spoken to a chap who has done some gears for me in the past and will look to close the gear ratios a little if necessary.

The aim really is to increase the number of 250s in the CRMC 500 Aircooled class. A mate will probably ride this one and I'll be out on my other 250. Outside of that I'll probably take a look at BEARS as well
 
#18 ·
The drum is ok but it's the same one the Ducati had the first year I rode it at the MGP. It just about survived short circuit racing but after one lap of the mountain and the huge amounts of buttock clenching that went with every downhill braking area showed it wasn't up to the job. I'm pretty sure it's in Martin Hudson's Motobi now so it may be ok if you can get the weight down!
The only sensible way to get to 250 with one would be increasing the stroke. They are already over-square so you don't want to be any bigger on the bore.
If I go that far with it will do the same as the Ducati and design a 6 speed box for it. As for engine tuning in my head I've already jumped to the extreme end of things and come up with everything from casting up new barrels to get a more useable bore size to changing con rods and firing order!!!!! It won't get that far, yet!!!! I'm not very good at leaving things alone! :doh:
I'll be at CRMC Brands if you're there I'll come and find you.
 
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