1979 Suzuki X5 Long term rebuild

Originally Posted by mister c

Thanks for the comments. I think that I'm going to have to rebuild the engine again. I thought that I was lucky that she ran with such an old crankshaft in, but have been having problems with carburation.
The bike ticks over fine & runs great after 6000 rpm, but is really fluffy up to 6k. The only thing I can put it down to is the crankshaft oil seals as I've set the carbs as per the manual, then set them as well as I could to no avail. The way finances are at the moment & with Winter on its way soon, I dont think it will be done until next year

What a pity, it is a very nice bike, indeed you have made such a nice job of it that you have to fix it properly.

Have you pressure tested the crankcase yet? You are a very competent mechanic, so I’m guessing you know how. It would not take long to rig up some bungs, a pump and a gauge to check out each side with the bike still in the frame. That won’t help fix the issue, but you will know what and where it is. At the very least you will be able to identify whether the issue is with an outer seal or (I suppose much more likely) an inner seal.

I rather assume you changed the outer seals on both cylinders as you were building up the motor, but depending on the results of the pressure test I wonder whether it might be worth changing both again. I don’t know that particular engine, but it looks like it is piston ported (well, no disc valves anyway) so the outer seals will be a really simple (and cheap) job.

Good fortune.

A


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[Craig380]

Originally Posted by mister c

Thanks for the comments. I think that I'm going to have to rebuild the engine again. I thought that I was lucky that she ran with such an old crankshaft in, but have been having problems with carburation.
The bike ticks over fine & runs great after 6000 rpm, but is really fluffy up to 6k. The only thing I can put it down to is the crankshaft oil seals as I've set the carbs as per the manual, then set them as well as I could to no avail. The way finances are at the moment & with Winter on its way soon, I dont think it will be done until next year

That could be the spannies causing the fluffiness ... it's a sweeping generalisation but if a stroker starts easily from cold and isn't burning gearbox oil, the crank seals are usually fine. And smaller engines will show the effects of slightly off carburation more than a bigger engine.

It's dead easy to raise / lower the needles in those carbs, have you tried moving the needle clip to see if it improves things?

It's also easy to makes a quick test of whether it's rich or lean at mid-range rpm and medium throttle openings - just give it half choke. If it runs with less fluffiness, raise the needle. It it runs worse, lower the needle.

Good luck, I hope you can sort it without having to do open motor surgery.

[Dave20046]

Looks great Mister C!

[mister c]

Originally Posted by Othen

What a pity, it is a very nice bike, indeed you have made such a nice job of it that you have to fix it properly.

Have you pressure tested the crankcase yet? You are a very competent mechanic, so I’m guessing you know how. It would not take long to rig up some bungs, a pump and a gauge to check out each side with the bike still in the frame. That won’t help fix the issue, but you will know what and where it is. At the very least you will be able to identify whether the issue is with an outer seal or (I suppose much more likely) an inner seal.

I rather assume you changed the outer seals on both cylinders as you were building up the motor, but depending on the results of the pressure test I wonder whether it might be worth changing both again. I don’t know that particular engine, but it looks like it is piston ported (well, no disc valves anyway) so the outer seals will be a really simple (and cheap) job.

Good fortune.

A


Sent from my iPad using Tapatalk

Originally Posted by Craig380

That could be the spannies causing the fluffiness ... it's a sweeping generalisation but if a stroker starts easily from cold and isn't burning gearbox oil, the crank seals are usually fine. And smaller engines will show the effects of slightly off carburation more than a bigger engine.

It's dead easy to raise / lower the needles in those carbs, have you tried moving the needle clip to see if it improves things?

It's also easy to makes a quick test of whether it's rich or lean at mid-range rpm and medium throttle openings - just give it half choke. If it runs with less fluffiness, raise the needle. It it runs worse, lower the needle.

Good luck, I hope you can sort it without having to do open motor surgery.

I will give both a try & let you know how I get on. I tried upping the jets to compensate for the spannies, but it ran worse. I will try the needles as an easy option 1st. Cheers people

[Bibio]

Lovely

small observation, to me its running a bit dry for a 2t e.g. not enough smoke. if the bike has a tank and pump for the oil try testing the output of the pump or if its new barrels then set the pump to "Run In" for the first 500 miles or so.

do a "plug chop" and check the plugs.

or it might just be you haven't ridden a 2t for a while...

[mister c]

Originally Posted by Bibio

Lovely

small observation, to me its running a bit dry for a 2t e.g. not enough smoke. if the bike has a tank and pump for the oil try testing the output of the pump or if its new barrels then set the pump to "Run In" for the first 500 miles or so.

do a "plug chop" and check the plugs.

or it might just be you haven't ridden a 2t for a while...

I don't trust the oil pump, so am running it on 40:1 premix. When I left the MOT station I did "give it a little" (I'm still running it in as it's had a rebore) & I couldn't see too much behind me. I started sing "Purple Haze" in my head

[mister c]

Right, quick update.
The carburation is sorted (well, almost). Apparently, the good old Japanese like to mess with different size carb needles & needle jets within a 2 year lifespan, I had the wrong combination, hence why the bike wouldn't run right.
Using a magnifying glass showed that I had the wrong needles fitted after I noticed that I had 2 different sizes in my spares pot.





So, with the carbs removed, I fitted the new jets & needles, fired the bike up & went for a short ride. She's running 99% better, but still runs on a little when I come to a stop, so just need to adjust the mixture slightly & she should be right

[Craig380]

That's great news. Those needles on the left of the pic aren't really needles at all, they're more like pop rivets

[garynortheast]

Great stuff! Any chance of a vid of a fly past on the open road then Col?

[mister c]

I let my son have a little tootle up his road last night, so videoed it. The bike seems to be running okish now, but I should have rebuilt the crank as the centre bearing is quite noisy now. Obviously 40 years of non use has taken it's toll. She's coming off the road over the winter, so I'll probably strip the engine & send the crank away to Grampian in Liverpool for a rebuild ready for the summer next year.