All gurus please help!!!!

After experiencing the fun to be had on my KLX, a buddy of mine picked up an 06 with a 351 convert and Mikuni pumper, 9k miles.

The bike ran ok, (didn't idle well, and hard to hot start without throttle), but I figured that these were all just carb related and an easy fix. It was also spitting a little coolant from the overflow now and then. Besides that it ran strong.

He's put about a hundred miles on it since purchase, but then there was today...
We were just heading out for our first trail ride only a mile or so out on the streets, when all of a sudden it started to sputter and loose power. Finally it just sputtered out and quit. When trying to crank it over it would spew a sweetish (not Swedish) smelling white smoke, and fun little white smoke rings out of the HMF. It wouldn't so much as try to fire again until it cooled down a bit.

So we head back to the shop, (he did the walk of shame if you know what I'm sayin'). Back at the shop we remove the carb to see if it may be the culprit but all looked well. The spark plug had a nice coating of black soot, and was replaced.

With fuel back in line, we fired her up and she ran great, better than ever really, for ten minutes or so. Then back to the smoke show we went followed by the loss of power and finally she sputtered out.

Next we drained the coolant to inspect the impeller and look at the thermostat, but no stat was to be found! We were thinking that maybe it had been removed as part of the trefiveone refit, but weren't sure, so we left it out.

Now we were thinking that maybe there was an over heating condition causing coolant to enter the combustion cycle at some point once the coolant circuit built up enough pressure. So coolant back in, we fired her up with the fan wired to run continuously. Shortly there after, we were once again signaled that the Pope had indeed been elected. So we shut down the operation and now here I am.

My current thoughts:

With my very limited knowledge of MC power plants, it seems to me that the bike is building excess coolant pressure, and leaking some of that pressure into the combustion chamber through a gasket or some other passage, causing a loss of power followed by shut down. (Water smokes white, right??) The oil looked good through the sight glass, (not milky thus not mixed with coolant), and it was just changed a day before.

I'm thinking that a top end/mid engine rebuild is in the near future, but I could really use some expert opinions. All opinions are very welcome.

Please let me know if more information is needed.

 

I'm no mechanic, but 2 questions lept out at me:

1) After running it again, is the spark plug black again?
2) Did you try take a sniff of the white smoke to see whether it had a strong pertol (or gasoline) smell?

The reason I ask is that white smoke can also be a sign of flooding or way too rich fuel mixture (I base that observation on a flooding prone pickup truck we had in my youth). If your plug is black again so quickly I'd assume it's something more to do with air/fuel.

Also, if it is indeed coolant leaking via a gasket into the combustion chamber, would some of that not also get into the oil and make it nice and milky? Might be worth draining the oil just to have a look see.

Hmmm. The hard starting might also support your theory though, coz water in the combustion chamber would damage the rings (wouldn't it?) making it lose compression and be hard to start. Any chance you can test the compression easily with the tools you have at your disposal?

 

I'd be lookin' at the head gasket. Thermostat removed to compensate for the extra heat build up and boiling coolant.

 

+ 1 on the above.
Have seen a few cars with blown head gaskets including my own Subaru a year ago and that's what this sounds like.
Your local bike shop will be able to determine this in minutes.

 

Yes, it is the head gasket. What style HG is in this bike? Old style copper, or new style steel?

When I had the old copper HG's I blew two of them. Same symptoms as your bike.

Call BB and get a new steel woven HG, or call comedic, I believe they make them. Fortunately it's only a couple hour job. Drain all fluids, flush coolant, flush oil, replace HG, and you should be OK.
Don't start it any more till you fix it.

 

Arctra - We didn't pull the plug again, but that would have been a good idea. I'll pull it and have a looksee. Also, the smoke had an odd sweet smell to it.

If it was a flooding carb issue, would this have any effect on the them of the bike? It seems like the carb would be flooding all the time.
--------------------------------------------------------------------------

Acole - How would a MC repair shop determine a HG failure? Pressure test? Is it something we could do at our shop?
--------------------------------------------------------------------------

Cousin Larry - I don't know the manufacture of the 351 conversion; do they all use the same HG? Which gasket are we talkin cause there is that spacer between the head and the block that appears to use the same gasket?
--------------------------------------------------------------------------

If the engine sits for a few days as is, will some damage take place due to corosion?

Thanks everyone for your input. Anymore ideas, tips, etc. are welcome.

Edit: I just spoke to Mr. Blue, and he is sending out a new head gasket as well as tuning tips for the Mikuni. Mr. Blue is a top notch fellow in all aspects of his business it seems.

Another question: Why is coolant spitting out of the overflow? Weird.

 

A shop can do a pressure leak-down test with the engine idle. However, I have seen certain gasket and crack issues only manifest themselves when the engine is at operating temp.

Coolant in the combustion chamber can rust and pit the cylinder in a steel liner like the 351 has if it sits for some period. How long that is?...not sure.

That "sweet smell" and white smoke sure sounds like coolant.

 

All the other guys above are correct, your buddy has a blown head gasket.
No need to do further testing at this point, the head must come off.
The sooner the better, like the Candyass said above the BB 351 uses a steel cylinder sleeve and that can rust/pit very quickly if there's any coolant in the cylinder.

--
Mikko

 

blown head gasket, the sweet smelling white smoke it burning anti freeze

 

+1 ....