1969 Johnson 40 HP - Reed valves?

[The Starcraft Enterprise]

Engine runs great, just came out of the shop. But when I have it full throttle it takes longer to get to full speed. A few waves and bumps and the engines revs a little a time. Good this be reed valves? If so, where are they?

 

[tx1961whaler]

Re: 1969 Johnson 40 HP - Reed valves?

No, if it runs great it is not the reed valves.
I don't quite get what the problem is.......

 

[jbjennings]

Re: 1969 Johnson 40 HP - Reed valves?

No, if it runs great it is not the reed valves.
I don't quite get what the problem is.......

Ditto on both...
Just curious-- why do you think there's a reed valve problem? Reed valves serve no function past about 1/2 throttle.

 

[jimmbo]

Re: 1969 Johnson 40 HP - Reed valves?

Reed valves serve no function past about 1/2 throttle.

I would love to heard the rationale for that one

 

[F_R]

Re: 1969 Johnson 40 HP - Reed valves?

Yeah, I went straight up when I read that. But when I came back down, I figure he means they can LEAK pretty badly and still run at high speed. But broken or missing??

 

[jimmbo]

Re: 1969 Johnson 40 HP - Reed valves?

Even leaky will cause a loss of compression in the crankcase so how would the cylinders get a fresh charge?

 

[boobie]

Re: 1969 Johnson 40 HP - Reed valves?

I've seen mtrs run with broken reed valves at WOT but wouldn't idle worth a darn. To much spit back through the carbs.

 

[HighTrim]

Re: 1969 Johnson 40 HP - Reed valves?

I've seen mtrs run with broken reed valves at WOT but wouldn't idle worth a darn. To much spit back through the carbs.

I have seen that exact thing a couple times as well.

Regarding the issue, is your prop hub spun?

 

[jbjennings]

Re: 1969 Johnson 40 HP - Reed valves?

Yeah, I went straight up when I read that. But when I came back down, I figure he means they can LEAK pretty badly and still run at high speed. But broken or missing??

Yes, that's what I meant. How the heck would one ever get it started if a reed valve was broken or missing. It would never happen. WRONGLY stated on my part. sorry OP......

 

[jimmbo]

Re: 1969 Johnson 40 HP - Reed valves?

I guess it could run on the remaining cylinders but probably like an engine that lost spark to one cylinder

 

[boobie]

Re: 1969 Johnson 40 HP - Reed valves?

If you have a 3 cyl mtr with broken or missing reeds in one cyl it will start and run at wot but won't idle. Been there.

 

[The Starcraft Enterprise]

Re: 1969 Johnson 40 HP - Reed valves?

Could there be a blockage in the fuel hose which leads to the gas tank? When it's at full throttle and there's a delay in response and than when I hit a wave or bumb, that will even jump the RPM's up. It's almost like there's a piece of junk clogging something up.

 

[The Starcraft Enterprise]

Re: 1969 Johnson 40 HP - Reed valves?

Some people have been telling me that. But if the hub is spun, I would probably still hear the RPM's witout the power. I am hearing RPM's increase with speed. Unless the prop itself throws out RPM like engine noise. How would I check/fix that?

 

[tx1961whaler]

Re: 1969 Johnson 40 HP - Reed valves?

You can check for a spun prop by drawing a line w/permanent marker across the center of the prop hub to the outer part of the prop. If the line on the center hub does not stay lined up with the outer part (under load) then the prop hub is spun.

 

[lindy46]

Re: 1969 Johnson 40 HP - Reed valves?

I'll bet you have an intermittant coil problem.