2 stroke help. Please.

[cookie_7]

Hi, my 1999 yamaha 30 hp 2 stroke (3 carby) has been running rough and cutting out lately. Done a compression test on all 3 cylinders cyl 1 : 140psi, cyl 2 : 140 psi, cyl 3 : 70psi. I check cylinder 3 inside, i noticed it has very bad scored marks. What causes this? Not enough oil? Wear? Old age motor?

Are 2 stroke motors easy to rebuild? Is it a big job?Can someone reconmend a good outboard machanic.

Thanks

[rayke1938]

If it will take a rebore you will be up for rebore costs plus 3 new pistons and rings.

You may be able to bodgy it up with a second hand piston and a new set of rings.

The bore will be scored because of a broken ring.

Depends on motor I know some motors have chrome bores and if they get scored the motor is totaled.

Cheers

Ray

[tomartomau]

Sorry to hear about that, as a rule there is an allowable 5% between compression between cylinders, clearly there is an issue with the one you identified. It could be a number of things. As for fixing it yourself, well if it was me I would take it somewhere (I do impeller/pump myself and other general servicing but a powerhead is another matter. You may need specialist tools, confidence and ascertain exactly why this occurred otherwise it may occur again if not properly diagnosed.

I guess you have three choices as I see it,

1. Get a quote on a repair

2. Compare quote to a new motor (trade in current motor)

3. Purchase another motor secondhand.

Yours is not the "CV" so when pricing a new one make sure you are not comparing to a CV model.

Here is a link that explains some of the failures associated with a 2 stroke.

/>http://www.smellofdeath.com/lloydy/piston_diag_guide.htm

All the best and keep us posted.

[cookie_7]

Sorry to hear about that, as a rule there is an allowable 5% between compression between cylinders, clearly there is an issue with the one you identified. It could be a number of things. As for fixing it yourself, well if it was me I would take it somewhere (I do impeller/pump myself and other general servicing but a powerhead is another matter. You may need specialist tools, confidence and ascertain exactly why this occurred otherwise it may occur again if not properly diagnosed.

I guess you have three choices as I see it,

1. Get a quote on a repair

2. Compare quote to a new motor (trade in current motor)

3. Purchase another motor secondhand.

Yours is not the "CV" so when pricing a new one make sure you are not comparing to a CV model.

Here is a link that explains some of the failures associated with a 2 stroke.

/>http://www.smellofdeath.com/lloydy/piston_diag_guide.htm

All the best and keep us posted.

Whats the different with my model and "cv" model?

[tomartomau]

I don't own a 2 stroke but from my understanding Yamaha make a CV model which is "Consumer Value" [2 piston] and a 3 piston which apparently runs a lot smoother and costs a bit more. Not 100%, someone else on the forum will verify or correct me.

[Bi_polar]

His motor is the Hi-Teck 30...I have one here too.

I would say that you'll need a re-bore.

Did you do the compression test hot or cold?

[cookie_7]

His motor is the Hi-Teck 30...I have one here too.

I would say that you'll need a re-bore.

Did you do the compression test hot or cold?

I done it when it was cold. Re bore and new piston rings, i hope.

Have you had any issues with yours?

[Bi_polar]

As long as they don't have a chrome bore you'll be ok.

i don't know much about the internals.

Ring Yatala Yamaha...i've had great experience with them and their ability to give free advice.

I've had no issues with mine but i have only just got it from my father and he bought it new.

He probably only ever has had it at half throttle.

I'll be selling it soon but it is on a Quintrex tinny.