Electrical Help please.

Having decided to get back into dirt bike riding after a 10 year lay-off
(married, mortgage, house, kids.... etc) I pulled my old XR250 out of the
shed.

Trouble is I can't start it. It used to start from cold after about 6
kicks, and first kick when hot.

Checked the obvious: I've cleaned out the carb, put new gas in, the is heaps
of compression, valves are not stuck.

There is a spark but it's not the brightest. Had the local bike test the
coil. They say that's OK. There isn't an audible click like you get with a
really
good spark.

I don't want to start swapping parts as that gets a bit expensive if I guess
wrong.

I'd appreciate advise on the following:-

- Is there a way to determine (measure) if the spark is bright enough?
- Does anyone have any diagnostic tests for mags and black boxes?

If I have to start swapping, I'd start with the black box. Question is, do
I <have> to buy a genuine Honda one (which I believe are expensive) or is
the a generic accessory part that I can use?

James

jamesatracingdrivesdotcom

 

Very true; my tlr200 starts and runs reliably, but the spark
is inaudible and invisble in normal daylight. The bike _is_
relatively sensitive to an over-rich mixture, and it's doesn't
take much to flood it.

It can be hard to distinguish too much from too little fuel. One
easy test would be turn off the fuel, drain the carb and try a
bit of starting fluid. If the bike fires you have spark, if not
there's a good cause to suspect ignition trouble.

hth,

bob prohaska

 

I've tried starter fluid. Not even a hint of firing.

 

I've been really careful to clean them all out.



James

 

Makes no difference. It's not only the jets that give the problem. It's
also all the horrible little galleries, nooks, crannies and so in inside
the carb.

This is a real problem with modern unleaded fuel, which has all sorts of
additives and stuff. The volatiles evalporate, leaving a horrible mess.
After 10 years of standing, I'd expect:

a) To have to get the carb ultrasonially cleaned or

b) Throw the carb away.

Seriously. In the last two or three years I've had to jettison carbs on
at least three old bikes I've been resurrecting and source decent
known-to-be-functional replacements (in one case, a brand new carb).

 

<Snip>

It's the carb.

 

Hmm, that's a bit discouraging, but possibly not decisive.

Starting fluid can't help if the mix is already too rich.
Did you drain the carb first? If so then I'd begin to suspect
the ignition.

bob prohaska

 

I'd agree in suspecting mixture problems, but I'd also check any
rubber 'boots` or gaskets in the airway for leaks. If that checks
out, I'd try spraying the passages in the carb body with 'gunk` or
brake cleaner, and then soaking it in a closed jar of raw gas for
a day or two in the hope of dissolving out any accumulated varnish.
There's no guarantee, but it has been known to work.
Best of luck,
Pragmatist - "R75/5 forever!"

 

P.S. To previous post:
If there's a vacuum fuel cock, check the vacuum line!
I once spent an interesting afternoon trying to diagnose a
friends no starting problem that turned out to be caused by
air leaking into the carb from a cracked vacuum line.
Pragmatist

 

Good advice. As was the other post.