Couple Q's about 4hp Rude 4736B/4706B

[restornator]

1. I did cold compression test. Peak on both cylinders is ~40, neither cylinder holds that compression for any more than 1/10 second. This is the first time i've checked compression. I can't get more than 1 revolution and and a proper test calls 5-8. Does the motor suck, or how do i test on this little thing?

2. I can't get more than 1 revolution on the comp test because my rewind starter is weak. The string doesn't zip back, it sorta crawls, so i have to wait 5-10 seconds before the next pull. I disassembled it, nothing was broken, spring was in good shape, reassembled with the spring coiled as much as it could. The string zips back in, but now i can only get a 2ft pull. How do i adjust this thing? i've had to wind the damn spring up 8-9 times already, and its a pain in the ***.

3. The motor is 4736 standard gearcase, i'm converting to the weedless gearcase. The only thing left i need to swap is the copper water tube, but it wont come out from the upper exhaust. also, the grommets are same part #, but the current tube fits real loose into the pump housing on the weedless drive. Are these copper tubes the same diameter?

 

[tashasdaddy]

Re: Couple Q's about 4hp Rude 4736B/4706B

copper tubes are the same. be sure the weedless has the rubber gromet in the water tube socket.

easiest way to test compression on those is to use a socket, in a battery operated drill. 3/4 inch socket, on the flywheel nut.

makes one heck of an electric starter, saves my arm.

 

[restornator]

Re: Couple Q's about 4hp Rude 4736B/4706B

yeah, i bought a socket drive for the power drill, haven't used it yet. But why won't this thing hold any compression?

 

[kbait]

Re: Couple Q's about 4hp Rude 4736B/4706B

Can you wrap a rope around the flywheel? That'd give you more spins. Don't know about the not holding compression, but if you get over 50 on your tester, it should run fine.

 

[restornator]

Re: Couple Q's about 4hp Rude 4736B/4706B

i did cold compression test on a non-running Tanaka 3.0, got 120 psi. It also held its compression. I wonder if the previous owner took apart the crankcase at one point and forgot to install piston rings? i have no clue

 

[F_R]

Re: Couple Q's about 4hp Rude 4736B/4706B

i did cold compression test on a non-running Tanaka 3.0, got 120 psi. It also held its compression. I wonder if the previous owner took apart the crankcase at one point and forgot to install piston rings? i have no clue

Darned if I know what you mean about holding compression. Are you saying you can bring it up against pressure and it bleeds away very quickly? Well, I reckon it would if you only have 40psi. The rings simply are not sealing it. Should have more like ~80

 

[restornator]

Re: Couple Q's about 4hp Rude 4736B/4706B

Darned if I know what you mean about holding compression. Are you saying you can bring it up against pressure and it bleeds away very quickly? Well, I reckon it would if you only have 40psi. The rings simply are not sealing it. Should have more like ~80

Yeah, that is exactly it. I am looking at having to open the crankcase and inspecting this motor. I am already going to assume there are no rings. Some genius must have really f'd this thing up. I already found the rewind starter assembled incorrectly.

 

[Don Hansen]

Re: Couple Q's about 4hp Rude 4736B/4706B

I doubt if you would get 40 lb without rings. Before you tear the block apart why don't you try taking off the exhaust cover plate. It's that large cover on the left side of the engine. While turning the engine over by hand you will be able to see the rings, 2 on each. piston through the exhaust ports.

Here's something else to consider. Maybe the rings and cylinder walls are extremely dry. Try squirting some oil into each cylinder. I like to use fogging oil because it comes with a straw and I can spray towards the cylinder walls.

Don H

 

[restornator]

Re: Couple Q's about 4hp Rude 4736B/4706B

Okay i can do that first. Where do i spray the oil from? should i just remove the cylinder head? i am not worried about gaskets now that i can make my own.

Also, how easy is it to take out this crappy CDI ignition and use the traditional magneto?

 

[F_R]

Re: Couple Q's about 4hp Rude 4736B/4706B

Okay i can do that first. Where do i spray the oil from? should i just remove the cylinder head? i am not worried about gaskets now that i can make my own.

Also, how easy is it to take out this crappy CDI ignition and use the traditional magneto?

Crappy, huh? Well everybody to his own opinion I guess. Fact is, the crappy CDI works better and is more dependable than any old magneto. Are you old enough to remember when cars needed points & plugs every 10,000 miles? Now plugs go 100,000 miles and there are no points. Of course you have to pay somebody to fix it if it does bust.

 

[restornator]

Re: Couple Q's about 4hp Rude 4736B/4706B

Crappy, huh? Well everybody to his own opinion I guess. Fact is, the crappy CDI works better and is more dependable than any old magneto. Are you old enough to remember when cars needed points & plugs every 10,000 miles? Now plugs go 100,000 miles and there are no points. Of course you have to pay somebody to fix it if it does bust.

the only reason i say its crappy is because i have no experience testing electrical components. plus its more expensive to replace. CDI still has 2 coils, plus a trigger coil and a power pack.

 

[Don Hansen]

Re: Couple Q's about 4hp Rude 4736B/4706B

You squirt the oil through the spark plug holes. Try to aim the oil at the cylinder walls. I like to set the motor on the floor, or tilt it up if it's mounted on a boat, with the spark plug holes facing up so the oil spreads evenly around the piston. Any oil should work but I like to use a thin oil so it can flow and coat the rings and cylinder walls.

As far as the ignition goes I suggest you compare part numbers in the BRP parts catalog on the internet. 1977 was the first year for the CD ignition so if you compare the part numbers for 1976 with yours you will see what you have to replace. I think you'll find that it won't be cheap.

Don H

 

[restornator]

Re: Couple Q's about 4hp Rude 4736B/4706B

i took the exhaust cover off. the gasket is burnt and flaky, but with it off, i used the drill and got 90 psi on both cylinders, and it held. no extreme leak down. also squirted some J/E 2 cycle oil in there.. I am going to go ahead and replace the head gasket too. I purchased the service manual on ebay, so i can diagnose the ignition system. i'll do another cold test with the new gaskets installed