Honda-SOHC

You say new coils are they pattern and if so are they same ohm rating as original, no i dont know from memory what that is

The new ones are pattern from Yambits, they are the same Ohm rating.
I have the original ones as well, the primary and secondary resistance readings of all of them are in spec.

No difference in behaviour between the two sets.

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

First ride was underwhelming to say the least.

In neutral, the bike was running nicely, idling at 1200, and stable.

Under load, the minute I hit 3500 revs it started to stutter and backfire, it felt like fuel starvation.

I read lots of forum posts, that the bike needs to run a bit rich etc, but no amount of playing with the mixture and idle helped much.

I was trying to narrow down the issue.

I had new plugs, all the leads tested good. I had cleaned the carb, I knew I had fuel, the timing was correct, so i was fairly convinced that the condensers were the problem,

Two new condensers this morning, and wow its a different bike. Idle is better, no stumbling or backfiring all through the rev range. Finally I can ride it without thinking about breaking down

Maybe I missed it, but have you checked your valve clearances and reset the cam chain tension yet?

After doing that to my CB550K it quietened down considerably.

Quick update:

She is now running very nicely indeed.

New plugs, cleaned and reset the points,  retimed it, cylinders 2 and 3 were well out. Checked and adjusted all of the valves, and reset the cam chain tension.

Changed the oil and oil filter.

My only observation is that the exhaust is venting quite a lot of water from the pin holes. I am putting this down to me only idling the bike. ( I cant ride it until it has new tyres and the paperwork back from DVLA etc). Any thoughts on this? I am hoping it will stop when I can take  it for a proper ride.

I started to dive into the seat today, and discovered that the floor pan is totally rotten on the edges, so will probably source a new one from DSS.

Plan is to keep it as stock as possible, with original paint etc. That may not be totally possible but we shall see.

Noted on the electrics, but so far mine actually seems to be better than i expected.

the factory that made is about one mile from where i live. they also  made cement mixers in the 60-70 factory now gone supermarket on site now . i agree well made british engineering .

It will likely last another 100 years if looked after. I am just a sucker for old engineering!!!

Whether it is a Ransomes Lawn Mower, a Myford Lathe,  Fobco Drill, Startrite Bandsaw etc etc.

I guess that is also why I am attracted to the older Honda's as they are built beautifully, and need to be cherished.

Nice looking bike Julie.

You have the front fender stay