Ideas for a project

[Hywel]

Hi!! I finish uni in a few weeks and want to learn more about bike mechanics over the summer. I'm a complete new jack to this therefore I would like something simple, so I could get my head around stripping and re-building the motor, possibly with improvements made in the process. My only criteria is that I'd like it to be vaguely relevant to the types of bikes I will be mostly riding for the foreseeable future... pretty much 4 stroke inline 4 sports bikes.

So, gimme some ideas for a very cheap bike that would be a good starting point for learning this stuff.

Also, how epic a tool-arsenal would I need to strip and re-build a small / small-ish four stroke engine?

[skatefreak]

Depends if your looking at just top end or all the way down (splitting cases, flywheels and such).

I did some pretty comprehensive top end work on a single 125 sohc 4t with not much more than a good socket set, bottle neck pliars and filo gauges.

As for a project, i myself am thinking over the summer to try and find a CBR250 to rebuild for experience and i fancy one heh.

I have an NSR125 engine to rebuild and sell on (surplus to the nsr i have) but that wont take long...

Older CBR250, 4 stroke, in line 4, not looking to pricey although i havnt come accross lots knocking around...

My suggestion as thats what i'm looking for *grins*

Best regards

-Jvr

[Hywel]

Yeah something I can use when it's back in one piece would be good and I bet those CBR250s are a laugh in the corners although something tells me I should start smaller. Like a little 50cc single or something, dunno.

I'll start with the top end but eventually wanna get through the whole thing, just to see how it all works and goes together more than anything else.

[skatefreak]

To be honest with you i recon a 250 would be good, in line 4 so basically a mini big boys engine.

The 4 stroke single i took appart was good as although it was imposing it tought me the basics and was pretty straightforward.

I recon it wouldnt be to much of a jump into a multi cylnder engine, anything smaller would get pretty fiddly and not so closly related to bigger bikes, anything much bigger though and i'd suspect you'll start investing more money...

The cbr250'd look like fun to ride and allegedly rev silly high, i'm on an nsr125 at the mo and it'll be a move up for me

Check out some rebuild thread/pages with pics and info or even a manual (not made it quiet that far myself heh).

Hoping someone will chime in with a little more knowledge soon though

Best regards

-Jvr

[skatefreak]

Been plodding through the internets and have come to the conclusion the CBR250's no longer exist

Well they do but there arn't many around and seem tricky to get hold of

Does anyone know of any more common in line 4, 4t 250cc sports bikes around? Am quiet keen on this configuration.

Best regards

-Jvr

[Guest]

You could use a 400 cc in line four as a project all the Japanese manufactures produced models,

or any 250 twin will give you the experience you need,

As for the tools required, Workshop manual, good quality socket set, Spanner set, torque wrench, inner and outer cir-clip pliers, feeler gauges, rubber mallet,vernier gauge, valve spring compressor impact driver allen keys , shed load of patience

the workshop manual will tell you of any specialist tools you need, platiguage, bearing pullers torx bits etc,

joining a owners club forum is a good idea, can be very helpful if you hit a problem that the manual cannot solve,

[Guest akey]

IMHO you couldnt do much better than the huble C90, easy to get hold of, loads of spares and depending what you want to do can be the start of a really fun pit or field type bike.

I have raced C90s in 4 hour enduros including MX tracks. CB100 forks fit straight in!

Depening what you want to do with it (road or field) there are a number of options, but its a nice simple engine with simple electrics that you can really get into, there are loads of bolt on bits, especially if you go down the monkey bike route (which are usually powered by a C90 engine) so there you go it could be a complete ground up project and could become a road bike (monkey bike guise).

I may even have the odd bit still laying around but if you want any ideas or pic of our old race bike let me know, or go have a look at some of the monkey bikes that have built.

[Bill_on_a_bike]

If you wanna start really simple do top end rebuilds on either 2 strokes OR 4 strokes with push rods. Push rods are ancient technology that everyone forgets BUT the trusty CG used them for a long time (they might still be I'm not sure). Nothing's more of a Faff than having to do everything hanging on to a timing chain to stop it flopping in to the crank case.

Tools, basic set of spanners and sockets, do get a torque wrench though. If you're dealing with valves get a compressor for them too, makes life alot easier