[RichM1983]

Hello all.

I'm new around here and need some help from the experts. A friend of mine has a 99 450s and it smokes BAD! If it sets a while it will start up and not smoke for maybe 10 secs and then it looks like a smoke screen. It is a huge amount of smoke. I can't even believe the plug doesn't foul immediately. The worst I've ever saw. Below is a list of what I've tried.

1. We tore it down and the gaskets looked bad. I thought the oil was getting in from bad gaskets so we changed those out with new OEM Honda. Still smoked like a steam train.

2. We checked the compression. It was 90psi. From what I've read that was normal. Although I've read conflicting reports on that being normal. The cylinder looks good and has good cross hatch still. Not groves or bad spots.

3. I double checked the ring gaps in the cylinder. I didn't check it with a gauge but it looks acceptable based on what I've seen in other engines I've worked with.

4. I put in new OEM Honda valve seals. The valves didn't seem to have any slop in the valve guides. Valves seat well and they don't leak.

I was told by the guy I'm helping out that it was running fine until he was riding it down a long steep pipeline right away. It started pouring the smoke half way down.

My last cheap resort is new OEM rings. If that doesn't work I guess we'll get a new piston, rings, and cylinder.

Am I in the right direction or am I missing something. I don't want to throw money down the drain but he wants it fixed.

Thanks so much!

 

[RichM1983]

Here’s a pic.

 

[SamUK]

Here’s a pic. View attachment 149195

Looks like your going to need a top end rebuild to me. Sometimes compression readings can give a false indication due to the auto decompression system.

Have you got a photo of the spark plug at all? Or even the top of the piston (or combustion chamber) from when you stripped it down last?

 

[RichM1983]

Looks like your going to need a top end rebuild to me. Sometimes compression readings can give a false indication due to the auto decompression system.

Have you got a photo of the spark plug at all? Or even the top of the piston (or combustion chamber) from when you stripped it down last?

I didn’t get pics. I did go ahead and order all the OEM parts to rebuild the top end. Hope it solves the issue. Once I rip it apart I’ll get some pics.

 

[shadetree]

did you ever check the oil rings ?. while you have the top end off, make sure to check the connecting rod for any play at the wrist pin area, as well as any play at the bottom of the rod at the crank. engine oil is not over filled...right ?. oil filter installed backwards ?. please do not try to re-use the new/old gaskets you just purchased !, replace with new all over again..or you will be right back to square one in no time !.

 

[RichM1983]

Well I put in all new gaskets, piston, and rings. The smoke is nearly gone. I think maybe the bore is out of tolerance from wear.

 

[shadetree]

Well I put in all new gaskets, piston, and rings. The smoke is nearly gone. I think maybe the bore is out of tolerance from wear.

if your rod is bad ?, everything your doing will be for nothing. anytime you work on a top end, you should start from scratch, do it right the first time, or dont do it at all.

 

[RichM1983]

if your rod is bad ?, everything your doing will be for nothing. anytime you work on a top end, you should start from scratch, do it right the first time, or dont do it at all.

The rod is good. Elaborate how that would cause it to smoke? I'm not sure how that works?

I'm working with a budget. Hard to spend that much at once.

 

[shadetree]

The rod is good. Elaborate how that would cause it to smoke? I'm not sure how that works?

I'm working with a budget. Hard to spend that much at once.

pretty simple, if the rod is bad ?, and your cylinder is out of round ?, your rings..including the oil rings !, will let oil by-pass to the top end of piston, and cause your engine smoking. if your on a tight budget , then your not going to be able to correct any of this. you must spend the cash to replace/fix what ever it needs to make it right, if you do not do this ?, all your time and money you toss at it will be from nothing.