Honda-SOHC

Hi All,

I put this on the XS400 forum, but it seems pretty quiet, so i am posting it here as well.

I know it is not a Honda, but it is an SOHC twin.

I picked up a 1980 XS250 at auction a month or so (sight unseen), no history, no idea when it last ran, a total punt to be honest, but its lockdown and I need something to keep me occupied.

Anyway it turned up, more or less as expected, tired, filthy (lots of dried clay on the frame), but only 14k miles.



Anyway I have worked through it, and done the following.

New plugs
New coils
New condenser
New leads
New caps

I have spark ( it seems ok, i say ok as I am not convinced its that strong, but its there)

I have static timed it with a test light, and all seems good

I have fully stripped and rebuilt the carbs, I have an ultrasonic cleaner, and I am comfortable that they are good enough to start the bike at least.

Compression is a bit on the low side, around 100 psi on both cylinders. So i took the head off, cleaned and lapped the valves, Pistons look good, i covered them in oil to see if it would leak past the rings, and 48 hours later it had not moved. So i am calling the rings good for now. Compression did not change after clean up, but I still think its enough to start. It easily blows my finger off the spark plug hole on the compression stroke if I hold it there.

The starter motor is very sluggish, cleaning up all the wiring I have managed to make it run a little better, but a replacement is on order

The problem though, using either the kick start or the starter motor is that it cranks, but it has never even popped or coughed, the plugs are wet from fuel from the carbs.

I have also tried starter fluid in the carb, and even direct in the combustion chamber, absolutely nothing at all.

So to date, it has not created a combustion event at all.

My gut is telling me it is spark, and that under compression it is not firing. I have an inline spark plug tester and it does look weak in comparison to my other bikes.

I am now at a loss, i have spent hours checking wiring, coil specs, etc.

Everything checks out.

One other thing is that the kick starter only seems to engage in the second half of its travel, is that normal?

Perhaps the combination of my weak starter, or poor kick starter, it is not getting enough oomph, but again my gut says poor spark.

So please, any ideas, no matter how off the wall are welcome.

Cheers
Matt

Hi All,

I am Matt from Surrey, pretty close to Box Hill for those that know of it.

I love all kinds of bikes, and have done a number of restorations over the years. Currently i have a Bandit 600, a Ducati 900ss, an 88 Honda CBR600F Jellymould and a Norton Atlas.

Yesterday i succesfully bid on a Jan 78 Honda CB550 K3 ( i think it is a K3 not a K4), but will confirm when i actually get the bike.

It looks to be totally original with approx 28k miles, and has not been on the road since 2005.

Plan is to assess and do what it needs , but with as light a restoration as possible and keep it totally original. And then use it.

Pictures will come soon, and i will start a restoration thread.
Cheers

Matt