HELP! Engine idles high then bogs down

[chapapadap]

Ok im new to this forum and hoping to find some answers. I have a 03 Blaster that was running awesome until about 2 weeks ago. When riding the trails i noticed that it was acting funny so we took it back home to check it. When you start it it would rev up really high and i would have to kill the switch. I took the carb apart cleaned it and no difference. I then took the reed cage out and found a broken reed. So i replaced the reeds yesterday and fired it up and it still doesnt run right. Now it seems to idle ok for a min but then wants to die. If i give it gas it either revs and kind of sticks or it wants to bog down and die. The only engine mods are a full Bills pipe and the Boyesen reeds.

 

[Quadman1]

Check Tors system, parking brake. Have you leak tested?

 

[harley1-5]

x2 on the leak tast

 

[chapapadap]

Ok so im on my lunch break and just did a compression test and got around 70psi. My friend rode it quite a while with broken reeds last ride. Will that fry my top end? Havent done a leak test other than spraying carb cleaner while running. Noticed a very small leak where the header meets the exhaust bit its very small.

 

[chapapadap]

Also tors and parking break are removed.

 

[Quadman1]

Time for a top end... And also fix that leak before heat cycles.

 

[harley1-5]

do a leak test before you tear it down that way you can fix any possible leaks at the same time

 

[Blaaster]

Even a small leak in the header can stop some of the expelled fuel charge returning to the cylinder and make for a lean condition.

It surprises me that you are able to start the engine with only 70 psi compression, did you have the throttle wide open when you kicked it?

I am going to be a parrot but, leak test before you pull it apart.

 

[chapapadap]

Even a small leak in the header can stop some of the expelled fuel charge returning to the cylinder and make for a lean condition.

It surprises me that you are able to start the engine with only 70 psi compression, did you have the throttle wide open when you kicked it?

I am going to be a parrot but, leak test before you pull it apart.

The first time i did the compression test it was 70 and i didnt have the throttle wide open. The second compression test i held the throttle open and got 70 again. I dont have anything to leak test with so i tore the top end off and checked everything. The cylinder and piston looked perfect. I checked the top copper head gasket and it looked like brownish water or something might have been pulling through. The base gasket looked good. No tears or marks. would the top copper head gasket possibly be why i was getting these symptoms? Also can i put high temp rtv sealant around the copper gasket when i put it back on tonight?

 

[chapapadap]

Also i completely rebuilt everything in this motor about 4 months ago. Bottom and top end.

 

[Tocco]

The top gasket can cause the low psi, idk about the idle. Just replace it anyways, if it looks bad. Its cheap and easy.

 

[chapapadap]

The top gasket can cause the low psi, idk about the idle. Just replace it anyways, if it looks bad. Its cheap and easy.

I have gaskets on hand. Was wondering if i should use some high temp rtv sealant with the gasket when i replace?

 

[Tocco]

I have gaskets on hand. Was wondering if i should use some high temp rtv sealant with the gasket when i replace?

Not for the brass top gasket. Just lay it on the right way, and then torqe the bolts to spec.

 

[chapapadap]

While i have it apart how do u tell if the rings are bad? Is it possible thats giving me low compression?

 

[Quadman1]

Never ever re use a head gasket. It will cause low compression and possibly do more damage. Also do not put sealant on the head gasket. When you rebuilt the top end did you set the rings correctly?

 

[chapapadap]

Never ever re use a head gasket. It will cause low compression and possibly do more damage. Also do not put sealant on the head gasket. When you rebuilt the top end did you set the rings correctly?

Yes this bike ran great for a couple months. This just happened suddenly.

 

[Blaaster]

Also i completely rebuilt everything in this motor about 4 months ago. Bottom and top end.

Did you heat cycle and break the engine in properly before going WOT?

What oil do you use?

How long has the pipe been leaking?

You need to get the piston and cylinder measured to see if they are within specs.

Is there any crosshatching showing in the bore.

You can do a simple check to see if the rings are worn by placing them in the bore and observing if the ring gap is excessive.

 

[chapapadap]

Did you heat cycle and break the engine in properly before going WOT?

What oil do you use?

How long has the pipe been leaking?

You need to get the piston and cylinder measured to see if they are within specs.

Is there any crosshatching showing in the bore.

You can do a simple check to see if the rings are worn by placing them in the bore and observing if the ring gap is excessive.

yes i did heat cycle after rebuild. I noticed the pipe leaking a week before it started running like this. The piston and cylinder were measured before i rebuilt. No crosshatching.

 

[Blaaster]

If there is no sign of any crosshatching It says to me that there has been a fair amount of wear.

When crosshatching disappears lubrication of the rings diminishes and wear starts to rear its ugly head.

What oil do you use?

 

[chapapadap]

If there is no sign of any crosshatching It says to me that there has been a fair amount of wear.

What oil do you use?

yamalube for mix and Rotella T for tranny