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British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on Today at 06:52:13 PM »There's always more to learn....
Last night I left a clean bit of newspaper under the bike after I'd run it up briefly.

This morning....

I'm pretty sure the culprit is the pump , which is not a surprise at all.

But it's only a dribble, it's livable with for now.
Today's plan was to get a few more miles on the bike, by visiting a Cars&Coffee about 20 miles away, then heading over to the Selsey RNLI charity event.
First I topped up the oil and petrol

And while I was at it I spread a little silicon into the Monza cap rubbers

Then set off, not without a little trepidation I have to admit!
But the bike is transformed! Fuelling at pretty much any throttle opening as pretty damned good! :banana-wrench: :banana-wrench:
So many thanks to the guys who pointed me in the right direction! :obscene-drinkingcheers:
It does have a tendency to spit a touch after a prolonged period of constant small throttle opening (ie 30 zones and following dawdlers...), but once you get "on it" it's fine!
There's still a dribble of oil escaping from the push rod tube (inlet), but it was only a dribble.

On the way back towards Selsey, I even got lucky enough to get an empty bit of smooth tarmac and wound it right open! :angelic-green:
Chin on tank..... The needle crept round the dial...
68...
69...
70…
..
71!
72!
...
73!
:lol:
Flat out is maybe 75 on the Smiths! :lol:
But the engine felt happy doing it!
Obviously though, by the time I got back towards the coast roads, the traffic built up and it was back to pootling along at 40.... :roll: yawn.
The vehicle gathering at Selsey was (tbh) a little quiet,

The ride home was more pootling, which the bike still doesn't like, letting me know with the occasional spit and hesitancy, so I decided to try and give it a bit more of a go by hitting the A27 just for a junction.
And got a bit of a shock. I'd just wound it open again when the thing died on me! It felt like either fuel station or lack of spark, then it picked up, then died, then struggled on again....
By which time I'd reached the next roundabout and peeled off for home.
Very odd.
The engine was fine again at low speed, then I got lucky again and had a clear run to the house, so I opened it up for about 300 yards then cut the engine to roll into the driveway on a dead engine.
The result. Black, but dry, the insulator isn't completely black.

I need to review the plug condition photos, but I don't think it's that far off...
Just need to figure out if it's a tad rich, or a tad lean.
When I had it WFO previously I did try easing off a tad a couple of times, and the engine just seemed to roll off, rather than gaining or complaining.
More testing required methinks.
Note to self... Top up the oil on the side stand!

Obviously, the bike was parked on its side stand during the afternoon, and I think it started dribbling then, because the was a stain on the thigh of my trousers....
I also remembered that I had Sealey pressure testing kit, so took the opportunity to check the compression while the engine was hot.

Hmmmmm, that's actually a little lower than I was expecting...

I should have checked it the last time I took it out, to establish an early baseline. I think I'm going do the compression ratio test soon, so we'll see.
Last night I left a clean bit of newspaper under the bike after I'd run it up briefly.

This morning....

I'm pretty sure the culprit is the pump , which is not a surprise at all.

But it's only a dribble, it's livable with for now.
Today's plan was to get a few more miles on the bike, by visiting a Cars&Coffee about 20 miles away, then heading over to the Selsey RNLI charity event.
First I topped up the oil and petrol

And while I was at it I spread a little silicon into the Monza cap rubbers

Then set off, not without a little trepidation I have to admit!
But the bike is transformed! Fuelling at pretty much any throttle opening as pretty damned good! :banana-wrench: :banana-wrench:
So many thanks to the guys who pointed me in the right direction! :obscene-drinkingcheers:
It does have a tendency to spit a touch after a prolonged period of constant small throttle opening (ie 30 zones and following dawdlers...), but once you get "on it" it's fine!
There's still a dribble of oil escaping from the push rod tube (inlet), but it was only a dribble.

On the way back towards Selsey, I even got lucky enough to get an empty bit of smooth tarmac and wound it right open! :angelic-green:
Chin on tank..... The needle crept round the dial...
68...
69...
70…
..
71!
72!
...
73!
:lol:
Flat out is maybe 75 on the Smiths! :lol:
But the engine felt happy doing it!
Obviously though, by the time I got back towards the coast roads, the traffic built up and it was back to pootling along at 40.... :roll: yawn.
The vehicle gathering at Selsey was (tbh) a little quiet,

The ride home was more pootling, which the bike still doesn't like, letting me know with the occasional spit and hesitancy, so I decided to try and give it a bit more of a go by hitting the A27 just for a junction.
And got a bit of a shock. I'd just wound it open again when the thing died on me! It felt like either fuel station or lack of spark, then it picked up, then died, then struggled on again....
By which time I'd reached the next roundabout and peeled off for home.
Very odd.
The engine was fine again at low speed, then I got lucky again and had a clear run to the house, so I opened it up for about 300 yards then cut the engine to roll into the driveway on a dead engine.
The result. Black, but dry, the insulator isn't completely black.

I need to review the plug condition photos, but I don't think it's that far off...
Just need to figure out if it's a tad rich, or a tad lean.
When I had it WFO previously I did try easing off a tad a couple of times, and the engine just seemed to roll off, rather than gaining or complaining.
More testing required methinks.
Note to self... Top up the oil on the side stand!

Obviously, the bike was parked on its side stand during the afternoon, and I think it started dribbling then, because the was a stain on the thigh of my trousers....
I also remembered that I had Sealey pressure testing kit, so took the opportunity to check the compression while the engine was hot.

Hmmmmm, that's actually a little lower than I was expecting...

I should have checked it the last time I took it out, to establish an early baseline. I think I'm going do the compression ratio test soon, so we'll see.
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