Popping Engine

[GraffitiDan]

I took my blaster out for the first time this weekend. It was running pretty good but had a couple of weird things happen. Most I will probably ignore for now, but after getting it a bit wet I am hearing some bad noises.

When idling it sounds ok except every maybe 30-45 seconds there will be a fairly loud popping sound. Also there looks to be exhaust gas coming out from between the cylinder and the cylinder head.

When I give it gas and ride around in 2nd or 3rd gear it sounds ok except if I give it ~50% or more throttle. At that point it sounds almost like a piece of plastic slapping against another piece of plastic ... really fast.

I have absolutely no idea what is causing this, can anyone help here?

Here you can see a bit of wetness between the head and the cylindar:
DSC00411

Here is a close up:
DSC00412

And here is a picture of a space in the head where it looks like the popping / exhaust in originating from:
DSC00413

 

[ruthless_one3k]

Looks to me like you just need a new head gasket. Not a big deal really easy fix. Just make sure you torque it to spec. Not sure but I think its 20 foot pounds. And make sure you follow the correct tightening pattern. If you need help with the pattern let me know and I can look it up for you.

 

[89custom]

sounds like new head gasket. dont run it untill you replace it though. also, check the head bolts, could just be loose, but if its loose like that, probably messed up the head gasket.

 

[peacher213]

ya compression gaskets are useless once you loosen the bolts...(theoreticly speaking)

 

[jlsparky7]

As said above a few times. Head gasket. Easy fix.

 

[GraffitiDan]

Ok sounds like it's an easy job ... although I've never worked on the top end before. Do I have to remove the whole engine from the frame to do this? Are there any videos on it?

Also, while I've got the head off, is there anything I should check for ... like obvious signs something else needs to be replaced etc?

Thanks.

 

[specialized7]

All you need to remove is your gas tank and cover.
you probably want to drain the gas first, it makes it much easier.
once you have that off, there should be 6 bolts on top, undo them
the head should come off.
you can inspect now and see whatsup.
everyone says not to reuse the head gasket so you probably will need a new one, there pretty cheap.
ill dig out my clymer and get the torque specs for you

 

[custom2stroke]

since you pulled the cylinder and head off i would replace both gaskets. What kind of bike is that on the left side of your pic?

 

[specialized7]

i dont think he is pulling the cylinder off, just the head.
if there isnt a problem with the base gasket dont pull the jug off.
snap a pic when you pull the head off

 

[GraffitiDan]

This is the quad I'm working on. 2000 Blaster.

Ok yeah I only want to remove the head if I can. The base gasket seems ok from a visual inspection. They have a gasket at the local parts shop so I'll go pick it up later today.

I'll take some pics along the way so we can check if there is damage.

 

[specialized7]

sounds good , just report back with pics and info

 

[GraffitiDan]

Here is what I did:

1) Drain gas tank
2) Remove tank
3) Remove exhaust pipe
4) Disconnect and remove spark plug
5) Loosen head nuts in a star pattern
6) Remove head

What I found was that the top of the cylinder body (dunno what its called) and the bottom of the cylinder head were pretty gunked up with oil / exhaust. The spark plug also was nearly black, which I guess means its "oil fouled." I'll replace that along with the gasket. Maybe I also need to adjust the carb?

The cylinder walls actually looked really good, almost like a mirror. The piston head had a pretty good 'crust' of carbon on it. It was not 100% covered, but nearly.

Here are the pictures I've taken. Can someone take a look an let me know if I need to do anything.

Head Gasket Pictures

What I plan to do is:

1) clean bottom of cylinder head with degreaser and brush (not the silver, just black)
2) clean top of cylinder body with degreaser and brush
3) replace head gasket
4) replace spark plug

 

[specialized7]

Everything looks pretty good.
just change out that head gasket.
i would say your jetted a little rich, but i woudnt change that until you get the head gasket back on,start it up and do a plug chop.
Do you know what size jet is in there nowÉ

 

[GraffitiDan]

Also a side note, there is not a bolt missing, the nut did not loosen on that one, and the whole two-sided bolt came out. Looks like I should be able to just screw it back in when I reassemble.

 

[GraffitiDan]

start it up and do a plug chop.
Do you know what size jet is in there nowÉ

I don't know what size jet. Is there a way to check? I would assume stock, but the guy I bought it from rebuilt small engine vehicles, so he could have changed it out.

By plug chop do you mean just start it up for a bit and 'read' it?

 

[specialized7]

throw a new plug in a rid it around like you stole it then take plug out and read it.
and to get that stud back in there , use 2 bolts on top of each other and tighten it in.
As for the carb, just pull the 4 screws outta the bottom and slide it off, you will see a brass jet in there, it will say the jet size on it.

 

[mr_3_0_5]

you have to run the bike wot then hit off and the clutch at the same time then read it.

 

[GraffitiDan]

Woohoo! I cleaned everything, replaced the gasket, head, tightened to spec, and it fired up and ran the best I've heard it run! I still need to deal the sparkplug, but I don't have time today. But there is no smoke or splatter or anything coming from the head gasket, and no popping. Thanks!!

 

[specialized7]

no problem man, were here to help!