200cc race bike

[Couchy]

Here we go, a race bike build for the CRMC 200cc race class.

2 base bikes bought, CB125 chassis with XL185 engine bored to 200cc.

To do :

Engine build xl185, wiseco piston, ported head, racing cam and valve springs

Race exhaust

32mm carb no air box of filter

Total loss ignition

Chassis stripped down cb125


Alloy rims on existing hubs, Avon race tyres

Brembo caliper disc and master cylinder

Hagon shocks

Custom rearsets, seat and tank

Discrete traction control launch control and abs....

[cheb]

This may or may not be useful: https://sites.google.com/site/vpcrabtree/home/xr200

There's a category called bucket racing.

[Couchy]

Yup got that already

[cheb]

I thought you probably had.

[Couchy]

Picked up the XL185 donor bike today and it’s raised some issues. It’s not much of a strip and rebuild to make it a nice bike again. Initial plan was to take engine and sell bits off but that means another fairly rare bike is gone for good. Plan b could be use engine for now and rebuild XL ready to take engine back. I do have the CB125RS engine that could be built into a 200 as well. No quick decisions I’ll strip XL this week and have a think

[Le_Fromage_Grande]

You'd be better off with a Benly or better the CB200 twin cylinder

[Couchy]

First build finally started. Completely stripped down the cb125rs and put the parts I don’t need to one side and binned some of the crap.

Need forks yokes wheel hubs and swing arm. Forks came out easy and had brand new taper bearings in, the frame also has the same so they went straight in together, result.

Next up swing arm and rear wheel. Axle is solid but luckily it comes out the back of the swing arm so we can think how to get that out tomorrow. With swing arm put to the frame the frame is 2mm too wide. Machine shop next door took one look and some measurements and went off with the swing arm, going to take a little off each side and remove the standard rubber bushes and fit brass ones . Once I’m get it back I’ll drop into the blasters next door then give it a lick of paint.
Managed to build a bench from off cuts to build the bike up on.

The frame is now mine and also got a scitsu Rev counter from same fella.


Got the 185 engine on bench to strip tip end. All seems ok but I’ll get engine man to have a look tomorrow before we send barrel off to be bored and order camshaft. Also got to order pva ignition and machine shop will make a plate for lhs of engine to do away with generator.Apparently there’s a ti exhaust I can have and then it’s time to build before stripping for paint

[Couchy]

You'd be better off with a Benly or better the CB200 twin cylinder

Heavier, less power and more expensive to tune but intrigued as to why ?

[weeksy]

Nice work!!! What bodywork you going for?

[Couchy]

In early to complete engine stripdown, all went easy and nothing to report, head will go for porting camshaft and piston to order.



Next up chassis, forks are knackered so while I'm wondering what to do the ever helpful neighbour drops by and says they have a set of drum brake forks they raced with and they are same size as my disc brake ones hmmm. So he drops them off and I strip both sets. Amazingly the good stanchions from the drum brake ones go into the disc brake bottom of my forks. A quick rebuild and they are back in the bike with some 31mm forks also sent my way. They need seals but it solves the issue of forks and also of front brake as machine shop next door has a plate to fit the brembo to my forks

[millemille]

I like that only tool in sight is a large hammer....

[weeksy]

I like that only tool in sight is a large hammer....

Nah, I can see his reflection in the fork leg

[Le_Fromage_Grande]

You'd be better off with a Benly or better the CB200 twin cylinder

Heavier, less power and more expensive to tune but intrigued as to why ?

Should make more power and rev easier being a twin cylinder, but it is a heavy engine for a 200 as it's a sleeved down 250, I'm trying to think of something good that's 200cc and four stroke, my memory of XR200s and DR200s is that the DR was pokier, but that could have been down to lower gearing, I can't even think of anything with 4 valves per cylinder - though Suzuki did a 125 with a 4 valve head, there might be a 200cc version of that.

[G.P]

Honda's little 125 twin cylinder was pretty pokey - 16.5 bhp at 11k according to the spec sheets. Some breathing and a few more CC's should help that.

Mind you, won't the class be full of X5 suzuki powered bikes? - 23bhp out of the crate.....?

by the way, @Couchy, If you don't use the XL185, I'm potentially interested

[Le_Fromage_Grande]

Honda's little 125 twin cylinder was pretty pokey - 16.5 bhp at 11k according to the spec sheets. Some breathing and a few more CC's should help that.

Mind you, won't the class be full of X5 suzuki powered bikes? - 23bhp out of the crate.....?

by the way, @Couchy, If you don't use the XL185, I'm potentially interested

4 strokes only for that class, otherwise it would be full of KDX200 engined beasties, and be a lot faster.

[Couchy]

You'd be better off with a Benly or better the CB200 twin cylinder

Heavier, less power and more expensive to tune but intrigued as to why ?

Should make more power and rev easier being a twin cylinder, but it is a heavy engine for a 200 as it's a sleeved down 250, I'm trying to think of something good that's 200cc and four stroke, my memory of XR200s and DR200s is that the DR was pokier, but that could have been down to lower gearing, I can't even think of anything with 4 valves per cylinder - though Suzuki did a 125 with a 4 valve head, there might be a 200cc version of that.

The DR is after 1972, only Honda made a single before then from the jap makers. Any descendant of that engine can be used but only that engine. Identified by cam chain tensioner on crankcase not barrel. So 2 valve four stroke single it is. Maybe a 175 which is the most powerful twin with money thrown at it would work but it’s a risk when the single is proven

[Le_Fromage_Grande]

I didn't know it had to be pre 1972, that seriously limits what's available

[Couchy]

Piston arrived today so that’s gone with the barrel to be bored out

Finishing guy dropped off some of my parts too, so I built the forks up with new seals and dropped new taper head bearings in. Alloy rims on way then I’ll send them and the hubs off to be built. Once on the wheels it becomes a bit more real. Swing arm has been modified to be a narrower mount and has had some billet chain adjusters made, its then gone to be painted same as frame.

[Couchy]

Swing arm is back, brass bushes fitted and adjuster plates made. It’s been cut shut and machined then powder coated.
measured up for shocks and they need to be 400mm long to give me the same geometry as the standard cb125rs.

Wheels arrive tomorrow and with a couple of spacers that’ll be it for the rolling chassis dry build. I can strip it down then and send off the bits that need coating and anodising.
Also got barrel and piston back so engine build can start

[Skub]

Honda in KTM colours!