Advice/help needed

[Lias]

Hi folks,

A few weeks ago I jumped on my trusty steed and went to goto work, however it was very sick. Absolutely gutless and backfiring like a fat bastard on a diet of nothing but baked beans and cabbage soup.

Given I'm relatively mechanically clueless, I need advice.. lots of it.

I took it into a local bike shop, who after 2.5 weeks still cant definitatively tell me whats wrong. What they've told me is that it has "30% leak-down" in the rear cylinder. They've told me that they cant hear where the problem is which makes it harder to diagnose. They've told me that to diagnose it anymore they need to pull the engine out of the bike and take it to pieces. This will cost 4-5 hours labour, plus assorted parts to put it back together again, on top of the couple of hours its taken to figure out this much.

They've then outlined some of the possible issues, and rough costs to fix them. Cheapest option was "valves" at a cost of ~1800, up to rebore and new pistons at around 4-5k.

Now these are not small sums of money, which I simply cant afford to pay, but worst case could probably secure a loan for as I am gainfully employed even if I do already owe my soul to the moneylenders.

What I'm asking is
A: Do any KB'ers near Hamilton think they could do this all/some of this work(even if its just to open it up and say for sure whats wrong) at a reduced cost, or perhaps even for a few slabs of beer, bottles of bourbon or whatever.
B: Do these sound like reasonable estimates for the work, or should I shop around other bike shops in the area.
C: Assuming I could even find one (my bike seems to be quite rare), what sort of cost would I be looking at for an engine from a wreckers?
D: The bike is only worth around 6k (Same model/year with 18000km vs my 33km currently on tardme for 8grand). At what price of repairs should I walk away, sell it as is on tardme and just not be able to afford a new bike for several years and be miserable.

Thanks in advance for you time folks.

[ManDownUnder]

On the face of it I'd say it sounds like a stuck or leaking exhaust valve and the shop can't be arsed looking at it.

Take it to another shop and see if you get the same response?

The exhaust value leaking will
1) Drop comnpression as the mix bypasses it to exit down the exhause and
2) Allow burning gas down the exhause when it's ignited - hence the backfire, and lower power output

Not a conclusive diagnosis... but that's where I'd be looking.

[riffer]

I fail to see how a 2 cylinder bike with maximum 4 cylinders will cost $1800 for revalving.

I agree with MDU. Rear exhaust valve is leaking. More likely seal then guide at that age, but still - 30-odd thousand ks? Doesn't sound a lot of mileage...

I'd be thinking of getting a manual and doing the work myself and saving about $1500 bucks if I were you.

[Lias]

I fail to see how a 2 cylinder bike with maximum 4 cylinders will cost $1800 for revalving.

I agree with MDU. Rear exhaust valve is leaking. More likely seal then guide at that age, but still - 30-odd thousand ks? Doesn't sound a lot of mileage...

I'd be thinking of getting a manual and doing the work myself and saving about $1500 bucks if I were you.

I have the service manual, but i'm seriously mechanically challenged.. It pretty much all makes no sense to me.

[Ixion]

Take it to another shop. Those figures are absurd.

Rebore on a V twin, plus new pistons, and labour @ $60ph , maybe $1500 max .

My guess is you've burned or bent a valve (though a holed piston is possible). Maybe a grand at max, assuming a shop does it. Most of that is labour.

[Katman]

Have they definately ruled out an electrical problem? Have they tested the stator?

It doesn't necessarily sound like a mechanical problem to me.

[Lias]

Okay.. bikes been taken to pieces, had the valves done, and put back together. It now has power (yay!) and is rideable, but still has some misfiring in the rear cylinder.

This seems to be limited to certain conditions, if you have the clutch in or the bike in neutral, and sitting idle at the lights, it will misfire if you turn the throttle.
It also misfires if when your riding, you release the throttle suddenly.
Doesn't seem to misfire when riding normally.

Any ideas?

[MSTRS:Me]

Okay.. bikes been taken to pieces, had the valves done, and put back together. It now has power (yay!) and is rideable, but still has some misfiring in the rear cylinder.

This seems to be limited to certain conditions, if you have the clutch in or the bike in neutral, and sitting idle at the lights, it will misfire if you turn the throttle.
It also misfires if when your riding, you release the throttle suddenly.
Doesn't seem to misfire when riding normally.

Any ideas?

That now sounds like a carby problem. Possibly running lean. Which may have been what caused the valve problem before. Get it looked at, before it goes full circle.

[vifferman]

That now sounds like a carby problem. Possibly running lean. Which may have been what caused the valve problem before. Get it looked at, before it goes full circle.

That sounds eminently sensible.
Uh... we do do sensible here on KB, from time to time, yes?
I can't answer for your particular bike, but I know that on the FahrtSturm, the rear cylinder was (allegedly) tuned to run a little richer, as it gets a little hotter than the front one.
So check the carby thing, and also make sure there are no exhaust leaks (can cause crap running too). The carb could be just set a little lean at idle, but there are other things to look at too: air leaks, grunge in the carb jets/airways/bowl.

[Lias]

That now sounds like a carby problem. Possibly running lean. Which may have been what caused the valve problem before. Get it looked at, before it goes full circle.

Thanks dude, will get it into the shop :-)