Engine overheating and smoking a lot ?

barossi73 said:
Color looks safe enough,(to me at least).if the color is true in pic...a little rich perhaps
Sorry im not more specific but unless theyre in front of you its difficult,even then... they vary depending on oil type,last ride etc. General indicator only.
Any sign of metal flecks?
Fine grey ring around tip of center electrode is correct ignition timing
If there is some form of oil/coolant contamination the color/cond could be skewed a little also
Click to expand...

Yes, the color in the pic is the same as what i see when holding it.

Back to the LHS PV cover, how can water get there ? Never saw that before. Maybe condensed burnt coolant ? Worn cylinder head o-rings ? I'll check the coolant level again tonight and drain the oil see if i find anything.

I am inclined to take off the cylinder head for a better look/picture of the piston crown.
 
Coolant level was a bit lower than expected. Drained it and it smelled a bit burned.

Drained the carb, looked transparent like water (gas in the tank looks greenish from the pre-mix oil i use). It smelled like gas and was slippery at touch, most of it evaporated quickly.

Took the cylinder head off, here are the pics:

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So what next ?
Do I take the PV off and clean it all up ?
Do I go ahead and change the RHS crank seal ?
How did water get into the LHS PV box ?
Piston change ? Piston rings change ?

p.s. full size pics here http://imgur.com/a/ia9gc
p.s.s. bike/piston has overall 100 hours now
 
Drop your coolant and see what you find. Looking at your pictures it looks like your inner head o-ring has failed above the exhaust port. You can see some markings there, and in the pic the o-ring looks potentially damaged too (hard to tell).

Everything looks a little wet, but it hasn't been wet enough to entirely wash the piston clean or fill the cases up. Enough to make it run poorly no doubt.

Piston is showing some blow by too. How many hours on it?

I'd suggest pulling the piston and giving it a freshen up, the PV a clean, replace the gaskets involved, and see how she goes. Is this one of the new heads or the old sand cast job? Hard to tell from pics.
 
Jakobi said:
Drop your coolant and see what you find. Looking at your pictures it looks like your inner head o-ring has failed above the exhaust port. You can see some markings there, and in the pic the o-ring looks potentially damaged too (hard to tell).

Everything looks a little wet, but it hasn't been wet enough to entirely wash the piston clean or fill the cases up. Enough to make it run poorly no doubt.

Piston is showing some blow by too. How many hours on it?

I'd suggest pulling the piston and giving it a freshen up, the PV a clean, replace the gaskets involved, and see how she goes. Is this one of the new heads or the old sand cast job? Hard to tell from pics.
Click to expand...

I dropped the coolant, it looked bad for the amount of hours it's been in there and had a burnt smell to it.

Regarding the inner o-ring, i'm thinking the same. Both will need to be replaced.

Piston has 100 hours on it, sand cast head. I'm told by local mechanics that they usually change these pistons at 120 hours, but i don't race so i don't know if i should invest in a new one or not. Will measure it out and see from there.
 
Just replace it mate.

I do mine at 65-75hrs and I don't race. For the effort and cost involved in pulling the engine down to replace the rings alone, it's not much more to put a new little end bearing and piston in too.

Make sure you check the big end incase you've had water sitting in there causing issues.
 
Looks pretty normal for those hrs.i dont see any signs of detonation...so no damage at least...my best guess is a very small coolant leak or you have sucked a little water at some point.you could try a fresh set orings before you go deeper.did any of the headbolts seem loose at all?being able to run the engine with the rhs pv cover off(pipe on) is useful when checking pv operation.iv not had to go deeper than a top end on mine so best someone else offers advice from here if orings dont cure it
 
Cool, thanks guys. Will replace all the o-rings and gaskets involved.

Time to research on what solution to use for cleaning the carbon buildup.

Also while we are at it, i have read around here that at only 100 hours you guys recommend putting the same size piston in ? Mine came with size B cylinder from the factory so am i right to assume that a new size B piston will last me another 70~100 hours ? Or should i get C size piston ?

p.s. C size and bellow pistons are not available anyways (stock) unless i buy a prox/wiseco/etc. piston and i don't really want to mess with measuring and what not since they are made of other materials and expand differently under heat, and i don't have the tools or experience required for the job
 
since you're there, 100h are enough to change piston and be safe ;) go measure the cylinder too and choose the appropriate size... guess you'll stay on B but you never know... and that is the point really... be certain on what you're doing and change washers, gaskets and orings whenever you can because that is how you eliminate possible causes of error ;)
 
Any reputable workshop should be able to spec the cylinder bore for you, most likely at no charge (especially if you make a purchase of some consumable while in the shop).

Then order in confidence that you have the right part. I've personally gone with wossner forged pistons every time I've replaced one. Get them at a good price and had no issues with them.

As above, don't skimp in the process and pay attention to detail. Spending the time to do it right means it'll be done once, and done right. Be a shame to re-use a base gasket and have to pull it down a second time.
 
Mine was A spec,replaced with an A wossner at 70hrs (200)from new.no problem.you say you have 100hrs on it.is that from new?or has it had a topend previously?if from new the same spec will be fine.
 
barossi73 said:
Mine was A spec,replaced with an A wossner at 70hrs (200)from new.no problem.you say you have 100hrs on it.is that from new?or has it had a topend previously?if from new the same spec will be fine.
Click to expand...

Mine came with B spec from the factory, 100 hours from new (this is the first top-end job for me and for the bike). I'll check before ordering the piston, just to be sure.
 
Last edited:
Measured the cylinder bore last night:
- 0.008-0.009mm is the tightest spot i could find (the needle on the bore gauge changes direction right under the 0.01mm mark, very hard to approximate how much) in diagonal
- 0.02mm exhaust to intake (largest spot i could find)
- 0.01mm side to side

So in the end, same piston will go in. I will also rinse the coolant system with vinegar, new gaskets, clean the PV mechanism and remove any play. Hopefully it will all be good, will keep you informed with the process as I go along and the outcome (ride report) probably Sunday if all goes well and parts arrive soon enough.
 
Get engine extra clean.Leave the 't' coolant fitting on the head if possible.the gasket wont be in the set.remove exhaust spigot.be careful not to bend pv actuator rod.dont let the actuator plate turn clockwise when refitting the nut.you will find you cant remove/refit cylinder 'square'.tip cyl backwards slightly as it comes off the studs and on reassembly lead slightly with rear studs.any writing on rings goes up.ring gaps/locator pins in piston to the rear.check small end bearing is exact match to old.take extra care fitting retaining clips on gudgeon pin,its easy to slip and scratch piston.carefully start rings into bore as you lower cylinder.a little 2stroke oil on the piston skirts.be patient,dont force the issue and it will be all good
Pv gaskets can often be reused if they came off clean.then you have new spares
 
Found:
- oily white slime on the carb slide (witch would indicate water i presume)
- carb mouth where the air boot fits had a "leak", you could see where the dirt came in with water
- small pieces of dirt on the air screw
- no water in the bowl tough
- small pieces of dirt on the boot mouth

All of the above coupled with worn out piston and rings could have caused it right ?
 
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