[Timothy Ma]

Hello All,

I have been given a 400 burgman 2006 and cannot start it. I checked for spark, fuel pump and injector and everything is fine. After attempting to turn over the engine at the crank I noticed there was no compression. There is a compression release mechanism on the camshaft so I was wondering how does one check engine compression because from what I can tell I can turn this engine over by hand (lack of compression).
I think this is why it can't start. Either broken rings or bad exhaust valve or ??

Any advice would be appreciated.

 

[Buffalo]

According to the service manual you can do a compression test in pretty much the standard way. It says to hold the throttle wide open and crank with the starter for a few minutes.

 

[speedandstyle]

Turn by hand? Turning from where exactly? If you can rotate the crankshaft itself by hand without any tools then you have very low or no compression. If you are turning the variator it should be possible, although difficult. Is there any resistance at all when you rotate the crank?

I didn't know that the Burgmans had a compression relief valve - how exactly does it work?

 

[Buffalo]

The 650 does not but the 400 does. The compression release is on the camshaft. It has a plate that rotates and a pin in the exhaust lode that does something but the manual does not say exactly what and I've never pulled the camshaft out to examine how it works. If you have a service manual you can see a picture of it on page 3-37.

 

[Buffalo]

In the servicing section of the service manual it says it the compression is low it could be valves, rings, the decompression cam not working or the starter turning to slowly.

 

[Timothy Ma]

Hello All,

You can rotate the crank once you have taken off the transmission covers (where you inspect the belt). A 24 m.m. socket will do or such in my case just grapping the front variator and rotating it in the direction of the engine does it. There is some resistance but when the engine comes up to the compression stroke you shouldn't be able to move through this cycle.

But I wondered if the compress release mechanism is making it easier so I will do as suggested and check the engine compression. Trouble is I only have so many hands. Hold the brake, place the gauge in the spark plug hold and then finally press the starter.

What should be the compression anyway? Lbs/inch^2??

 

[Timothy Ma]

Oh I forgot...can you remover the cylinder head with the engine still in the frame? Can remove the cylinder head and the cylinder with the engine in the frame??

Just asking??

 

[Rustydust]

According to the service manual you can do a compression test in pretty much the standard way. It says to hold the throttle wide open and crank with the starter for a few minutes.

Um, you do mean a few seconds don't you? That would seem to make more sense.

 

[Buffalo]

Doing the compression test is easier if you have a compression gauge that screws into the sparkplug hole rather than one you have to hold. That is what I ended up buying to do a compression test on my 650.

The spec the manual gives is for a warmed up engine. Obviously you will not be able to do that if it won't start. Spec is 122-128 psi standard with an 88 psi minimum limit. I interpret that to say if everything is up to snuff you should be getting 122-128 but it should run with it as low as 88. Since you are doing it cold you will get somewhat lower readings.

 

[Buffalo]

Um, you do mean a few seconds don't you? That would seem to make more sense.

Yes, my old brain is showing

 

[Buffalo]

Oh I forgot...can you remover the cylinder head with the engine still in the frame? Can remove the cylinder head and the cylinder with the engine in the frame??

Just asking??

I've never attempted it but according to the manual both can be removed with the engine in the frame.

 

[speedandstyle]

Um, you do mean a few seconds don't you? That would seem to make more sense.

The way I was taught how to use a compression gauge was to stop once the needle refuses to move any higher. That might only take a few seconds with a single cylinder but it might take 30 seconds on a V8. The thing is it needs several compression cycles to get a full reading. Some gauges are better than others too.

 

[peelbrow]

I didn't know the 400 had a valve-lifter, but it seems like it's stuck on. Have you checked this?

 

[Timothy Ma]

I don't know how to check it. I have the valve cover off and I can see it but don't really know what to look for. I haven't performed a compression test because I would like to button it up and then use the electric starter to turn the engine over.

I don't have a compression tester that screws in so a bit clumsy.

Timothy

 

[peelbrow]

I don't know how to check it. I have the valve cover off and I can see it but don't really know what to look for. I haven't performed a compression test because I would like to button it up and then use the electric starter to turn the engine over.

I don't have a compression tester that screws in so a bit clumsy.

Timothy

I don't know about the 400, but all valve-lifters I have ever seen operate by holding the exhaust valve off its seat. If you have the cambox off you should be able to see if this valve is being held open because it will not move up and down when the engine turns over.

 

[Buffalo]

To test it the manual says it should turn smoothly and the pin that goes into the camshaft lobe should move with it. They are showing checking it with the camshaft out of the head so I don't know if you can check it without pulling the camshaft.

Here is the picture I scanned from the manual

 

[Timothy Ma]

OK I tried performing a compression test and I need one that screws into the spark plug. It didn't register pressure at all. So I think it maybe the decompression mechanism maybe part of this mysterious problem.

I also noticed that the tube that goes into the PAIR device (top of the engine) had a big crack. Could this be why it can't start?

I have no idea how the mechanism works. I should be getting the manual tonight from the owner and I will decide if I should tear down the engine further.

Comments are most welcome.

Timothy

 

[Timothy Ma]

OK just went to Ron Ayers to check out the camshaft pricing and there is no decompression mechanism pictured along with the camshaft. So even if I purchased the camshaft it appears it does not come with this replacement part. I looked through the parts (all the microfichs) and don't see this part.

I am guessing that this is not available??

Timothy

 

[Ralph M]

If it's been standing a long time maybe a valve as stuck,
I worked on industrial engines for many years and though
many of them had de compressors I never had a problem
with any, check the valve clearance if it is to big you could have
a stuck valve, squirting a little oil down the plug hole may get the
compression up and once it starts it is likely to sort it's self out,
again if it's not been run a long time change the fuel it can go
off if it smells like paint stripper then it definitely as.

 

[Timothy Ma]

OK thanks....I was going to change the fuel but draining it could be a problem. I will try what you suggested but this weekend its going to be raining.

Timothy