Need help again in good old Germany.
I played already a few days with the carb around to get the engine running right.(ī97 Explorer 500 ) At one point I had a thought that the valve clearance affect the bad running of my baby. When I had the top cover off,
I discovert that the cam from the exhaust valves where totaly gone. The cams for the intake valves are still okay. Can someone tell me why this happens. I just bought this ATV used and I donīt know what the pre owner did with it. Now I will contact partsland to send me a new camshaft. Hopefully they send parts oversea, than here in germany the parts and ATVīs are dobble so expensive like in US.

Wait now for your advice before I assamble the engine again.

regards from germany.
Reinhold

 

I dont know about atv's but i know about camshafts in car engines. The best advice is this, replace anything that touches the cam lobes. Make sure the oil in that engine has been changed (the old oil will have flakes of the camshaft in it...this may already have hurt other bearings in the engine). Check all the oil pasages that feed the cam and make sure that the bad lobe did not starve for oil to make it fail. Use the breaking lube that comes with the cam. The most important thing is that you adjust the valves correctly when you re-install the new cam.

P.S. some engines can be prone to eating camshafts (at least in cars ex.. the old chevy 305). you might see if this is a common thing for your quad.

 

Also... Thinking in reguards to a car / truck engine is the "break in" of the cam. A cam for a daily driven vehicle has to be held at 2000RPM for about twenty minutes to "break it in". I am assuming that a camshaft for a quad would have some type of break in needed. Might check with someone like Web Camshafts for this info.

Good luck.
Jes [img]i/expressions/face-icon-small-cool.gif[/img]

 

A new camshaft is coming now from partsland to germany. Hopefully it goes nice through the customs.
I like to have my weely fixed when the first snow falls here.

@ Sceiks
Shoud I flush the inner engine only a few times with thin oil and just check the compresion of the piston, or shoud I open also the lower crankcase and check the crank bearing and oil pump for damage?

@ jesbuilt
I just been on the homepage of web camshafts. I noticed that they offer a racing cam for only 155 $. Is this offer an new cam, or they just reweld and grind your old one. Will give them anyway soon an call for some hints for my small problem.

Iīm waiting now for my little shaft from US and a lot of snow from the top.

Reinhold

 

As to the question about rewelded cores or brand new shafts, I'm not sure what they use. Some companys offer both. It just depends on the grind of the cam your looking at.
As to the cleaning issue. If you are knowledgable with splitting the case on your bike, it would be a good idea. I had a Mustang loose a cam. I thought I had it cleaned out enough,but it wasn't. I ended up rebuilding the whole thing. So if you can get to all those little shavings, go for it.
What did you find out about a break in proceedure?
Good luck and have in the snow. Our snow left us about a week ago.

Jes[img]i/expressions/face-icon-small-cool.gif[/img]

 

If you have the oil filter that was in the engine when the cam ate itself i would cut into it and see what went through the pump and crankcase. If it is real small slivers (tiny tiny glitter) i would just keep checking the filter every time you change the oil, if you see anything at all that is of any real size it might be worth cracking it open. Since you live Abroad that might be an expensive thing to do. Flush your oil with normal weight oil A couple of times and keep an eye on the filter.

 

Cut the filter ! Never heard or thought of that one. Great idea. I'll have to remeber that.

Jes [img]i/expressions/face-icon-small-cool.gif[/img]

 

never mind..... deleted

 

You might want to also take a close look at the rocker arm for the exhaust valves - more than likely you will find the face of the rocker arm that rides on the cam lobe will be dished/scored/rough - which will result in premature failure of your new camshaft.

The #1 cause of the camshaft failure is due to lack of oil to the top end - that is why they suggest using 0W40 oil - it is thin enough to pump during the critical startup of a cold "dry" engine.

From what I've noticed over the passed few years, you can tell when a Polaris camshaft is starting to fail by a lot of kickback when starting (electric starting is almost like starter drag, rope starting feels like too much compression, or impossible to start manually) - just a little extra tip [img]i/expressions/face-icon-small-smile.gif[/img]

 

@quadwrench

Your right !! I had always a lot of kickbacks before the engine fired up. And it was verry hard to start it up with the recoil starter.

And again, your right with the rocker arm !! The chrome hardfaceing is gone and the contact area for the cam is now verry rough. Iīm now looking for workshop which restore the chrome hardface. Because, the money level in my pocket is now verry low.

@all
Thx for your good tips. Itīs a verry productive forum here.

Reinhold