Suzuki VX800 knocking/tapping ** Update**

[Jordee]

Hi,

I know this is going to be a difficult one, I'm a newcastle fan and nowt seems to be going my way today.

Anyway, My much loved suzuki vx800 has suddenly started with a tapping/knocking and loss of power.

The choke has virtually ceased to have any effect on engine revs, which bodes badly for the winter, And the right hand exhuast pipe (as your looking at the headlight, left hand if your sitting astride) has suddenly developed a huge scorch mark at its first bend out of the engine.

Oil levels / coollant are both fine, please help me.

jordee

[MarJay]

[Jordee]

Thanks for getting back, I can answer the questions you've given me, if that helps.

The noises appear (to me anyway) to be coming from the front of the engine, I have disconnected each spark lead in turn to see if one cylinder is causing the problem, and it isnt. The problem persists.

The noises are a metalllic tapping sound, not as harsh as a full on knock but definitely audible in a helmet, and can be "felt" when riding.

The noises occur when in any gear (including neutral) and are unaffected (seemingly) by engine temperature. The noises become difficult to hear at higher speeds, but I am fairly sure this is just because the bike itself is making more noise.

The reason I mention the choke was to correllate with the fact that I am sensing a loss of power about the bike. I similarly mention the following symptom, regardless of its direct connection (i dont really know whats what). Occasionally the engine will cut out as I brake for a light or something. Again, engine temperature seemingly has no effect on this, although a full tank tends to prevent it (fuel swilling away from the fuel line?)

I haven't tried running the bike on reserve to see if this cures the problem, but I can certainly do this tomorrow.

I dont know what else you may need to know, I'm happy to answer anything, I just dont know whats relevent.

Can I assume that since coolant levels and oil levels are good (and not decreasing), that I dont have an impending explosion on my hands? I need my legs, I use them a lot.

Would you believe that I'm a qualified electrician, and I have literally no clue...

[petemell]

It could be dirt in the carb float bowl fuel valve causing the carb to overflow, perhaps petrol is spitting back into the filter and this needs changing.

[Paddy Blake]

The choke cable is broke or the choke is stuck on all the time.The exhaust being of color would seen like the rear cylinder is not getting enough fuel so carb problem.
I think you have two problems.One is carb related and the other could be cam chain or cam chain tensioner.
You have noise from front cylinder and colored exhaust from the rear one.

Paddy

[Jordee]

The above posts both seem logical, and I'll check the advised issues tomorrow.

For reference though the discoloured Exhaust definitely is coming from the front cylinder.

[Paddy Blake]

It is not an air filter problem.Just cutting that out for you.

Paddy.

[petemell]

If there is dirt or water in the carburettor it will be worth checking the air filter while you're at it.

[MarJay]

I don't understand how a blocked air filter can be related to a knocking noise, or a blackened exhaust...

It does sound like you have two issues. Hopefully you haven't holed a piston from running too lean on one cylinder or something...
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Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[cestrian]

The air filter flagged in my mind too, as did a faulty carb and a valve problem. It's so hard to diagnose when you can see and hear the problem.
Then I thought "Isn't that a V-Twin motor?" ....and so it is.

So It's the downpipe from the front pot which is getting hot. I'd be checking the choke linkages to the carbs, I'd check the carbs too but don't make any adjustments yet as the front of the engine most likely runs a little hotter than the rear. It may be liquid cooled but it also gets plenty of cool air across it, unlike the rear.

[Jordee]

Had a good look round earlier today, and to correct a couple of my earlier statements:

The blackened Exhaust IS coming from the rear cylinder NOT the front cylinder.

As the bike has two air filters, is it correct to assume the front cylinder is fed by the front airbox, and the rear cylinder is fed by the rear airbox?

Really dont know where to start with this, is there someway I can remove a couple of bolts and get a better idea of whats happening? Or do I need to strip the engine?

[MarJay]

[baldy]

Does the front exhaust get hot? I bet that it's only running on one cylinder.
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One day i will rule the world, just not today.

[Jordee]

Thanks for all the help fellas, I know my inability to provide pics etc. is not helping the diganosis, but you wouldnt believe the rain we've had here lately.

If I can get a dry 10 minutes I'll take some pictures for further perusal.

I dont think the bike is running on one cylinder, as stated earlier I have removed each spark lead in turn, while the engine runs rougher when i do this, surely it would cut out all together when I unplugged the one running cylinder?!?

The airboxes are pretty awkward to get at, but I'll have a look as soon as this weather buggers off.

Cant remember who asked but Big Sam was let go because he's as appealing as a shrink wrapped turd.

He'll pitch up at West Ham just you watch....

[petemell]

Did the problem start straight away from starting from cold or was it when you were out riding the bike?

Or did it start going like this over a period of time?

[Jordee]

Hi, the bike developed the problem while riding.

also the bike is used quite regularly,

Occassionally gets a week off, but normally used every working day....

...bit like me really.

[cestrian]

Like Marjay, I'd be looking for differences between the air filters and plugs, also shining a torch down into the bores when the plugs are removed.
Sorry, I thought the front cylinder was connected to the right exhaust, not the left.

[Paddy Blake]

We are getting a lot of weather here as well.

There might be water in the carbs so turn off the fuel and open the drain screws at the bottom of the carbs to get it out.If you can drain it into a container to see if there is water in it then it would help.

Paddy.

[Jordee]

Hi,

New update to day, I know its been quiet.

But Having had the bike looked over by a qualified bike mechanic, he says the big end is gone, and that I should be looking for a new engine now at around £400.

Does this sound right? how much would I get for my bike at a breakers, would anyone trade it in?

Can I do a repair job myself or do I need too many specialist tools, are there any other options, what is the chance that he is wrong?

[MarJay]

[Pete.]

If the big-end is knocking then drain the oil into a plastic tray and inspect it for debris. A silver film floating on the oil, or golden granules in the bottom indicate big-end shell damage. It might be a little-end, rather than a big-end.
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Robby]

Head on over to www.vx800.net . A guy on there called Brian knows these bikes inside out.

The engine is I believe the same as used in the VN800, and more or less the same as one of the kawasaki 750 jobs. So getting a replacement engine isn't difficult.

However, these are tough bikes, and they have a crap inlet fuelling arrangement and fairly exposed electrics, so make sure it isn't a carb or sparks problem before pulling the engine apart. Do the oil thing recommended above though.

How often were you changing the oil? I found in mine that the gearchange went off after about 2000 miles on the same oil.