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Loss of power, broke down, won't start

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I've been out riding today and my XR400 has died on me, it started sounding different and felt it had lost power, 5 mins later it sounded worse and when I pulled over it stalled. Now it won't start again and the kick starter doesn't seem to build pressure like before, anyone any ideas or should I start with a compression test? I've had the top cover off and have done the clearances and set the manual decomp and all this has been perfect since, until now!! Thanks

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Check the easy things first.

 

Spark plug hasn't worked it's way out? Change it.

 

Check to see if the gas tank cap isn't venting properly. If the bike sits a while, cools off and then starts up, good indicator.

 

Jets in the carb or fuel screw hasn't fallen out.

Edited by Trailryder42

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Yeah def check the spark plug first. I replaced mine a few months ago. I think I had the original one from 2002 in there.

ImageUploadedByThumper Talk1446936447.794509.jpg

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It's brand new, only done 100 mile so doubt it's that. Will check it all tomorrow though.

The Kickstarter feels sloppy now too though, like it doesn't build up compression to TDC any more.

Thanks

Edited by alan0259

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I've read of people finding the lock nuts on their valve tappets loose or completely missing. I suppose that would allow the tappet to vibrate itself into a condition that could cause either a too loose or too tight valve clearance. If that happened on the right exhaust valve, you'd lose your compression. Easy enough to check by removing the tappet cover in the head cover.

Edited by Trailryder42

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Ok, took the valve caps off and had a look, all the lock nuts are still tight and all the valves are still in spec. every now and then when using the Kickstarter I feel and hear a slight mechanical crunch too.

Edited by alan0259

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Wondering if it's worth me buying a compression tester or if the lack of kickstart resistance is enough to suspect there's low compression?

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 every now and then when using the Kickstarter I feel and hear a slight mechanical crunch too.

 

That don't sound good. I agree with messat, drain the oil and look for debris. >>>>>>>>>>>>>>Will it be safe to do compression tests after I've dropped the oil?<<<<<<<<<<<Yes, there's oil still in the head and coating the cylinder.

 

When you turn the engine over with the kickstart, do you get big puffs of air coming from the crankcase vent line? With nothing to hold/build compression in the cylinder, as the piston moves up, that air has to get displaced to somewhere. Since the valve clearances are good, that means air is getting by the piston and rings, escaping into the crankcase.

 

What year model is this XR?

Edited by Trailryder42

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1999 XR400R.

When pushing the kick starter slowly it does make an air blowing sound but I've never noticed where it's coming from. But it's always done this since I've had the bike (couple of months).

I'll try and get the sieve out the wife's kitchen before i drain it!

Still worth buying a compression test kit too? Or if there's metal debris pull the top end anyway?

Edited by alan0259

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If there's metal debris bigger than glitter, as in chunks, doing a compression test is a waste of time. Tho having the tester for the future and adding to your toolbox would be nice.

 

Can you pinpoint the location of the crunching noise when you use the kickstarter? Is it coming from the kickstarter gears, somewhere in the trans or the top end?

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Ok I've just removed the oil filter and have drained the frame oil and oil from the bottom end.

There were around 4 really small shards of metal, I'd say approx 1mm and really thin.

It doesn't always make the crunch noise, I haven't been able to make the noise today so not sure what this could be, I just remember thinking "that sounds wrong" yesterday when I broke down.

So what could this mean?

Damaged piston and a top end rebuild needed?

I'm worried I'll have to take the bottom end to peices as well to maybe find more shards? I'm hoping I could just flush it somehow?

Edited by alan0259

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I'm assuming the shards are aluminum (non magnetic)?

 

I hate to say it's time to pull the cylinder, in case there's something not being revealed or that we're not thinking of. Altho pulling it isn't difficult if you have the tools.

 

It would be interesting to know what the oil strainer in the bottom of the engine has caught. It is accessed by removing the right side engine cover.

 

Wonder if you could have a broken piston ring. Unfortunately, anything that has to do with the piston means the cylinder has to come off to check.

 

Do you have a shop manual?

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Yes I have a manual, I've had the cam off before so I'm confident on pulling the cylinder off to expose the piston etc.

Been watching XR400 rebuild videos today too and it looks pretty easy knowing what I already know so do you think it's worth pulling it to visually see what state it's in?

I didn't check if they were magnetic or not, I'll see tomorrow. What does it mean if they are or aren't magnetic?

And yes that's a good shout about the oil strainer. I'll have a look at that too.

Thanks

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If there are no metal flakes or something unusual in the oil you can fill it back in

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Yes I have a manual, I've had the cam off before so I'm confident on pulling the cylinder off to expose the piston etc.

Been watching XR400 rebuild videos today too and it looks pretty easy knowing what I already know so do you think it's worth pulling it to visually see what state it's in?

I didn't check if they were magnetic or not, I'll see tomorrow. What does it mean if they are or aren't magnetic?

 

 

If the debris is magnetic it means they came off of steel parts.

 

You've ruled out the other possibilities mentioned earlier, so I think I'd break it down. When you get the head cover off, first check the condition of the auto decomp cam on the camshaft and make sure it's not sticking or broken. Make sure you don't have a sticking exhuast valve.

 

Before you remove the cam you have to remove the auto tensioner. I'm guessing your cam chain is the original. So go ahead and check how much adjustment the tensioner has left in it. Before removing the tensioner from the engine, take the screw cover out of the center and insert a screwdriver. Turn the driver to retract the tensioners plunger. Count how many turns from fully released to fully retracted. Then after you remove it from the engine, check it again to gage the difference. If there isn't any or very little, your cam chain is at or near being worn/stretched beyond the the abilities of the auto tensioner to compensate for. So you'll be looking at a new cam chain.

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I converted my auto CCT to manual when I first bought the bike. It had a noisy rattle from the top end (turned out to be the valves) but I thought the CCT may have been dodgy so I pulled it apart and used a long enough bolt and nut to make it a manual one and it's been ok like this.

I'll measure how far it's screwed in currently and will put it back to this when re-assembling it all as a guide.

Unsure how I can check the chain condition like this though...

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I converted my auto CCT to manual when I first bought the bike. It had a noisy rattle from the top end (turned out to be the valves) but I thought the CCT may have been dodgy so I pulled it apart and used a long enough bolt and nut to make it a manual one and it's been ok like this.

I'll measure how far it's screwed in currently and will put it back to this when re-assembling it all as a guide.

Unsure how I can check the chain condition like this though...

 

So you installed a bolt thru the center of the stock CCT and screw that in to extend the plunger? You have to be careful with a setup like that. If I remember right, the plunger shaft is fluted and a bolt won't push the plunger out. The bolt basically pushes the metal cap on the end of the plunger off, destroying it and it possibly falling into the engine. I would check it over good if yours is like this.

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