Bad block seal causing hiccup?

[redfury]

Hey all. I've been working a little on my 25hp Jonny ( 1990 ) and rebuilt the carb this winter. I'm getting a backfire and fuel pooling in the carb along with an idle that doesn't seem to want to change unless I just about close off the low speed circuit completely.

Anyway, I'm getting the impression that I've got a block seal that's going out. I'd really like to fix this motor, but I can't afford to throw money at the problem.
Time, I've got. Ability, I've got. knowledge is what I'm a little low on. I've got the manual and a compression tester ( basic ). I'm pretty sure I ran a compression test on it last year and it was fine. I'm going to pull the flywheel and see if any of the ignition components are showing any signs of wear before I go too nuts with this.

What I'd like to know is if there is a known seal that is common for leakage so I can get pointed in the right general direction.

Beyond that, I'd like to know what is involved in a crankcase pressure test...can I do it at home...what do I need?

 

[ezeke]

Re: Bad block seal causing hiccup?

Based on the symptoms, I would be looking for an air leak in the fuel system or carburetor gaskets. If the flywheel has been off, better check the key to make sure it is still in one piece.

The fuel leak is probably from the float valve not closing properly. If you have air and fuel actually blowing back into the carburetor, check your reeds.​

 

[redfury]

Re: Bad block seal causing hiccup?

Okay, I'll double check on that. The carb rebuild went pretty smoothly though, it was pretty clean when I pulled it apart, and the motor is running pretty much the exact same way as before the rebuild. I doubt the flywheel has ever been removed from the boat as it was owned by my uncle before my dad, and my uncle rarely used the motor. When I had the carb off, the reeds looked like they were all laying flat and I didn't notice any signs of cracks/metal fatigue.

 

[billybones]

Re: Bad block seal causing hiccup?

I'm sorry but how could you have forgotten a compression test? I have a.d.d.. THis would be like a major thing in day to day life.. You have a tester now would be the time to do another one... JMHO.. especially cause you can't remember what it was. well sorry i guess I am out of the info business. sorry for the thread....

 

[redfury]

Re: Bad block seal causing hiccup?

I forget because I did so many compression tests on so many different motors last year that I don't remember if I specifically did a compression test on this motor. Quite possible that I did not. I'll be certainly be double checking the compression. I'm merely wondering if anyone here had any experience with this particular range of motor and if there was a known weakness in one of the block seals that would be worth looking for, that's all.

Worst case scenario, I'll drag it down to the guy a few blocks away some monday when I have the gumption and have him look at it. He's an authorized Johnny Rude mechanic.

http://youtube.com/watch?v=XYvx2GbFyiU

This is what it ran like before I rebuilt the carb. It runs only mildly better. First things first, I know I need to get new plugs for it to at least eliminate them.

 

[redfury]

Re: Bad block seal causing hiccup?

Well, I had it running today. When warmed up, it was running really nicely. Smooth and responded well to throttle.

Let it sit and cool down and just couldn't get it to start ( it's been a hard starter since I got it ). If I put my hand over the carb and choked it enough to pool fuel in the carb, it would start and run fine.

However, I think I'm in need of a new impeller now. Had it running, spitting water out of the pressure valves and out of the tell tale, but the last time I got nothing out of the tell tale or the pressure relief

Gives me a good excuse to go through the lower unit I guess.