2008 Suzuki DF 70 (4stroke) : cracked cylinder head : worth replacing ?

[Tao]

Hi,

Sea water was mixing with engine oil.

Cylinder-head has cracks on the surface mating with the top of the block (which has no scatch).
Craks are only arround the area that face the two bottom cylinders (sea pics).

Any idea of the cause ?

Some friend says it could be sea water coming up through open exhaust valves (which apparently occurs on low mounted engines). But I'm sceptical : no damage on the cylinder walls or piston heads.

Is it worth replacing the cylinder head ($1600 bare) ?

Thanks


Here is some history about the engine that may help :
- 30 hours only, but stood still for 8 months, laid on one side with oil in. Pistons stuck when I got it ;
- removed power-head and cylinder-head. Found oil had made its way into the two bottom cylinders and had turned like varnish ;
- cleaned and freed pistons. Noticed craks on the cylinder head but not bits of metal in the cylinders or in engine oil. No scratch on the cylinder walls ;
- hooked everything back up with new gaskets ;
- Engine ran fine for 5 hours (checked oil every 30 mn). Then noticed sea water was mixing with engine oil.

 

[robert graham]

Re: 2008 Suzuki DF 70 (4stroke) : cracked cylinder head : worth replacing ?

Looks like corrosion problem, maybe a welder could build up those areas and re-surface? Might be worth a try before laying out big$$$ for new head. Some of the 4 stroke experts on here may have some other ideas for you. Good luck and let us know what you decide to do!

 

[Tao]

Re: 2008 Suzuki DF 70 (4stroke) : cracked cylinder head : worth replacing ?

Thanks.

Welding seems an option - depending on the quality of the welding : if bits of metal fall down in the cylinder, the engine's dead.

Has someone ever successfuly tried this ?

 

[Haffiman]

Re: 2008 Suzuki DF 70 (4stroke) : cracked cylinder head : worth replacing ?

I would have taken it to a machine shop and checked if possible to mill down to clean sealing surface for the head gasket.
Might look worse than it really is.
Go up yo 93 Oct, run the CO sensor to re-adjust injection and go boating!!

 

[Tao]

Re: 2008 Suzuki DF 70 (4stroke) : cracked cylinder head : worth replacing ?

Found a shop that says they can weld the head and rectify everything (head surface, valve seats, valves) for approx $800.

Seems quite a lot but I think I'll give it a try since bare new head is $1600 and I'd have to properly adjust the old valves to the new seats myself.
I'd rather leave that job to properly equiped professionals.

It will take quite a lot of time cause I need to send the head far from where I live. Will keep you informed.

I'm still interested in your ideas about the causes that damaged this cylinder-head...

 

[McSpadden]

Re: 2008 Suzuki DF 70 (4stroke) : cracked cylinder head : worth replacing ?

Tao,

I have a 1999 DF60 and pulled the head yesterday for the second time. These heads are made of inferior metal, in my opinion. Anyway, 800.00 seems pricey, last time I had mine fixed, filled and surface only, for $100.00. I plan to do the fill and surface again this time and will buy a Yamaha if it happens again.

 

[Tao]

Re: 2008 Suzuki DF 70 (4stroke) : cracked cylinder head : worth replacing ?

I do think these heads are made of cheap metal.

Any way, I did not have much choice since I live in some place where no one could fix it.
I sent it to the shop ; they filled the holes, replaced a valve and cleaned the thing.
It costed me ?400, that's a bit more then $500. With transport I took 45 days !

I reassembled the engine, with no problems.

The only thing I woud point out is the alignment pins between the engine holder and the block.
There are two. As it was when i disassembled and as it is said in the manual, one is supposed to go ine the block, the other in the cylinder head.

As my head hab been rectified and resurfaced, it ended up a little thiner. I could not but the powerhead back into place as the pin would not enter the hole in the cylinder head.
So I ad to use the third hole in the engine holder to put the second pin. Like that, the two pins are located between the engine holder and the block. I think this third hole is for that purpose, but they did not mention it.

For that reason, it's important not to tighten the cylinderhead bolts after the powerhead has been put back ont the engine holder. Tighten the head to 73NM first, like it's said on the book.


Engine's been runing fine since then. But I wonder for how long.
I'd definitely go for yamaha next time.
Besides, I believe you don't need to pull the powerhead on them to take appart the cylinder head !

 

[karlow1]

Re: 2008 Suzuki DF 70 (4stroke) : cracked cylinder head : worth replacing ?

Yea well, I'm working on mine currently, and you absolutely have to lift the power head to pull the cylinder head.
I'm fighting the water in the oil problem. The head does not look bad. there is hardly any pitting and no sigh of a leaky head gasket other than the oil issue. It passes the straight edge test and was running good. Tomorrow I will take a look at the block, and maybe finish pulling the short block to check the pan.

KP

 

[karlow1]

Re: 2008 Suzuki DF 70 (4stroke) : cracked cylinder head : worth replacing ?

Did you check the base of the power head for corrosion?
Did you check the zinks that are mounted in the head?
If you let the zinks go, the head will follow!

KP