Bought a used Scram and going through it. Not sure how many hours or type of care it had.

It was very hard to start and wouldn't idle when I got it.
I rebuilt the carb and it runs and idles now.. But very hard to start when cold.
The only way to start it is placing my hand over the breather port near the tank.
Once it's warm it will start with no problems. And runs fine around the block.
It does knock when it first starts up, but the knock goes away when it warms up as well. The knock is echoed through the cvt intake port.
I'm also pretty sure it is idling too fast, I have lowered it to the point where it barely idles, but still too fast for the reverse, cause it will die when going into reverse unless I use the override.

I ran a cold compression test and it didn't even move the needle. The needle bounced a few times but didn't even get to a number.

Any ideas on where I should start looking next. should I run a hot test?
Should I look at the CAM or look somewhere else.

thanks

 

Knock could be the front clutch spider wear. They can make a clacking noise and quieten as speed increases. You can pull the black wire from the reverse limiter and eliminate it all together then it shouldn't die in reverse,will have full power in reverse without having to push the over ride button. Compression test on this model since it has a decompression device on the cam should be between 50-80 psi on average with the throttle held wide open. Plus if you're not showing at least this check the valve clearance. .006 clearance intake and exhaust valves.
This leads to checking the exhaust cam lobe also as this model was affected on the soft cam lobe issues. If the exhaust lobe is ground down,could be the source of most of your problems. Here's the pics of a worn cam on a Scrambler 500.http://forums.atvconnection.com/pola...d-cam-pic.html

 

I looked and the cam and it looked ok, normal wear and all valves where working. I checked the valve clearance and the intakes where tight, couldn't even get a feeler in them. Exhaust was right at .006. I set the intakes to .006 and it fired right up.

Ran a compression test again and still couldn't get the gauge to move, only bounced the needle.. Might be a bad piece of crap from HF. Its the one that has the plug fitting on a rubber hose.. I don't think I can get a good seal by twisting that hose..?

I'll let it cool back down and test it again tomorrow to make sure it wasn't a fluke start.

thanks OPT.

 

OK, its been a few months and the bike has been sitting for a while(no time to ride).
Anyways..
I go to start it up last night and cranked and cranked and cranked.. and nothing.
I finally spray'd a little starter fluid and it ran on contact.
So I checked the fuel line and there was no fuel in the line. So that led me to the fuel pump line to the carb. I blew/sucked on that for a bit, heard the pump working, and poof gas was running to the carb.
once it fired up, the pump was working correctly and all was good and ran for a long time.
Question is, does this sound like a bad vacumm on the carb side, not actuating the pump like it should. or will the pump not work correctly if the carb feed line is empty, kinda like a siphon?
I believe this has been the bad start problems all along.
Even went out today and it started right up.
The carb leaks real bad, so I always have to shut off the gas.
I rebuilt the carb this winter, but I couldn't get it to stop leaking, with all the adjustments to the float etc.. never would stop the leak.
Any thoughts.

thanks

 

Take a Mityvac to the impulse(vaccum) line at the carb,unhook the fuel line at the carb and see if fuel flows under vacuum with petcock on reserve and on position. If it does have good fuel flow then sounds like you need to go back through the carb,clean it up,even if it had a new carb kit installed several months back, keep stabilizer in the fuel along with a battery tender to save the battery. Sitting up with the crappy gas we get now hurts them more than riding them every day.