1985 Johnson 70hp

[racerone]

A new motor is a very good option.

 

[cesandroid]

right and 7000 for the same size. i guess its a decision that its coming down too. tear it apart or look used maybe to keep cost down. Compression again tonight 122, 130, 124 ... cyl 1,2,3. mind you using a compression tester that you have to hold in the plug hole instead of the thread type. not sure if those numbers are borderline either. others welcome to chime in.

 

[Bosunsmate]

Replace your top seal. Flick it out with a screwdriver or whatever, anything you do is cheaper than a new motor

 

[Wkd179]

Its been a while but there was a modification required on the carbs for that model year. If I recall increase the idle jet by three sizes.Parts list says #28 increase to #31 and retest. Also be sure engine is up to temp

 

[cesandroid]

ok thanks wkd, but wouldnt increasing the size allow more air in. if i increase fuel by using the primer or decrease air than it will fire.

 

[racerone]

cesan are the jets in your motor for fuel or air ??

 

[cesandroid]

Idle is for air, bottom one is high speed for fuel. Bottom one actually is supply for both.

 

[racerone]

Are you sure ?

 

[cesandroid]

Hey racerone are you trying to help or not? Judging by all your comments, your not. Either help or get lost.

 

[Bosunsmate]

Hey racerone are you trying to help or not? Judging by all your comments, your not. Either help or get lost.

Id say he is, he just takes a bit to get used too lol Dutch or French i suspectainkiller:

 

[cesandroid]

Piston up side down?? Gimme a break, I'm not that stupid. If someone can explain the carburetor to me if I'm wrong by all means I'm listening. Guy at the marine shop said that orifice for low speed was for air. Looking at the fuel path I would agree. I've seen posts on older models about changing jets as well. This problem seems to be unique to Cyl. 1. On mine. Ill change the top seal because its cheap. I have the timer base on order as the readings were off so we will see.

 

[Dennischaves]

Are you sure it's a carb problem?

 

[cesandroid]

Carbs are switched and doesn't follow, so no I don't think its a carb problem. Problem sticks to number 1 cylinder at idle. Unless its missing at high speed too, but it sounds OK when I get past low speed.

 

[Bosunsmate]

Last wild card i can throw out is have you checked the top cylinder is warming up?
Other than that i can only think of the seals.
Good luck
PS upside down piston can relate to its orientation. If its upside down then the piston skirt will have the porting all wrong. It does happen that they are installed upside down on rare big stuff ups. Most pistons have like an arrow on the piston dome to show correct orientation for install. You may be able to see it if you look through the spark hole.
Upside down doesnt mean necessarily big end bearing facing outwards, if thats what you had thought he actually meant then id understand you being grizzled about it!

 

[cesandroid]

Hmmm, cylinder seems to be warming up like the others, OK, trying to understand the piston concept but not getting it yet. Will research that indeed and learn. Looking thru the holes I don't see anything different per cylinder. I see a dot for lack of a better term, on top of each piston. To me they look the same. I was reading about the looper concept of a dome like piston I think, with the intake and exhaust ports on the side wall. Thanks for your time bosanmate, I'll report back if I finally get it. PS yeah I thought that's what he meant. To me piston upside down is in fact crank side up.

 

[cesandroid]

Actually, thinking about it, do you mean piston 180 rotated and installed or is there sleeves on these installed wrong? Would taking the head off confirm this? Thanks

 

[Bosunsmate]

Haha yes crank side up is a funny thought you thought you were being accused of.
Ive only rebuilt a few motors, i just help out a few friends who get themselves into motor trouble, im otherwise toiling around as a farmer in New Zealand.
So ive no idea on the specifics on your motor sorry, some aces on here will. But if its a looper you definitely need them correctly orientated, ie not rotated 180degs. And yes cross flows too need correct orientation otherwise incoming fuel/air wont go up the cylinder. But the dot up the top sounds like they are correct. And yes i have heard people have sleeves rotate but again thats all new to me. Id imagine taking the head off would enable you to inspect for that. You could also clean out the cooling passages at the same time and plane the head on a piece of glass or a mirror with light sandpaper on it. That improves compression. So if you ordered a head gasket at the same time as the seal you would cover two possible causative issues of that cylinders problem

 

[Wkd179]

I believe they are fuel jets. (if there is a plug in front of them they are fuel...if no plug air jets)

 

[cesandroid]

The low speed orifice up top is for air. The gasket covers it but receives air from an opening on the lip of the carb. Side note, changed the top seal with no difference in cyl 1. Didn't think it would but an easy change so why not. Still waiting for timer base. Did pickup an intake, head and exhaust gaskets and will take apart for inspection. Don't think any of this was serviced as the paint is still on the original gaskets. At this point in the game I guess I'm not giving up. Sooner or later the odds have to fall in my favor.

 

[Bosunsmate]

Thats a shame the top seal didnt fix it. Keep posting what you find it to be, only so many stones to turn over