Carburetor question on restoration I’m working on 1992 40 hp MSHQ Yamaha

[Douglasdzaster]

Water leaks usually occurs at high rpm not at idle or muffs, go for a wot run with removed cowl and visually figure out if the leak comes from the cylinder head, exhaust cover or lower pan gaskets...

Happy Boating​

That’s the next plan. I’m watch the weather now so I can pick a good day. Been getting an unusual amount of rain and storms for this time of year.

 

[Douglasdzaster]

Water leaks usually occurs at high rpm not at idle or muffs, go for a wot run with removed cowl and visually figure out if the leak comes from the cylinder head, exhaust cover or lower pan gaskets...

Happy Boating​

Wasn’t able to get to the water yet so I checked bolts. I found several on the exhaust cover where not tight at all so I fallowed the numbers and torched them all. The bottom ones took the most. I’m hoping that was my leak. All of other bolts on engine where good. The bottom pan took a little as did the thermostat housing. But not much.

 

[Douglasdzaster]

Couldn’t make it for a lake test today so I thought I’d check out the idling issue and see if it dropped rpms again. Found another issue I need to ask about. While running water is coming out from around where the shift rod comes out of the leg. Also in front of that is a hole that drains water when you lift the motor and water is shooting out of that more than the tale tail. Along with a good amount coming from the upper exhaust port. Motor never over heated and was at operating temperature. Sea Rider what in the world is going on now. Do I have some bad seals or what. If I do have something wrong I want to fix it before going back to the lake. I really appreciate any advice.

 

[Sea Rider]

Understand your frustation with that Yammie, if the motor is squirting water around the middle/lower leg while running on muffs expect to see that scenario which it's quite normal. For better clarification, post a pic showing where is the water going out the exhaust port, or were reffering to the exhaust side cover ?

Happy Boating​

 

[Douglasdzaster]

Understand your frustation with that Yammie, if the motor is squirting water around the middle/lower leg while running on muffs expect to see that scenario which it's quite normal. For better clarification, post a pic showing where is the water going out the exhaust port, or were reffering to the exhaust side cover ?

Happy Boating​

Sorry I haven’t posted any pics yet. But I figured out what I was doing wrong. I was addressing an idling issue and wanted back pressure on the exhaust so I used a tank with a hose running in it. It’s just deep enough to cover the cavitation plate which I found out isn’t deep enough. Water came out of everything above. There’s 2 exhaust ports on the sides and the small square in the rear farther up under the motor. I can get pictures if you still need to see them.
Back to idle problem that I’m scared of because it may lead to the cdi. ($600)
While idling on muffs I noticed a small missing ( running a little rough) a few minutes after it was up to temperature the rpms dropped from around 850 to around 450. I quickly checked the temperature and it was 138. About a minute later it went back up to 850. I ran it the next day and it did the same thing except this time it died. Started right up with one pull. I shut it down and started checking things.
Compression 105 , 110 , 105. I started with the fuel tank and removed the fuel. It was clean and no water. The pick up tube is clean. I checked all connectors and clamps while inspecting the fuel line. Pulled the filter under the cowling and it was clean with no water in the fuel. Pulled the spark plugs and they all looked good and the same. I started the motor and pulled the spark plug wires one at the time and each one effected the idle the same. I cleaned all the grounds for the coils. I’ve ordered a tester to check the spark length. If that checks out I’m thinking about pulling the carburetors again Incase something got in one.
I’m still keeping fresh none ethanol fuel.
I have enjoyed learning and fixing up the old Yammi but some days I’m saying NOW WHAT! I have to figure this out so I can get it to the lake and run wot to look for the water leak. Hopefully re torquing the exhaust cover fixed that.

 

[Sea Rider]

Personally dislike testing any motor too long on muffs, tanks, should be tested at wot on flat calm water if possible. Remember, that's a 2 stroke motor and if tested too long at idle/fast idle will foul the plugs. Hope the mentioned retorqued parts will have cancelled the water leaks. If still seeing water on the pan, that gasket is shot. Were you able to carry out the CRC decarbon process ? if not go for it, should even the idle rpm...

Happy Boating​

 

[Douglasdzaster]

Personally dislike testing any motor too long on muffs, tanks, should be tested at wot on flat calm water if possible. Remember, that's a 2 stroke motor and if tested too long at idle/fast idle will foul the plugs. Hope the mentioned retorqued parts will have cancelled the water leaks. If still seeing water on the pan, that gasket is shot. Were you able to carry out the CRC decarbon process ? if not go for it, should even the idle rpm...

Happy Boating​

I’ve only had it out the one time when I took the grandkids. I’m trying to get everything right before the next lake test but you’re right I’m having to idle to much to do so. I haven’t decarbed yet due to all of the above. Can I do it at home , then change spark plugs or do I need to run wot as soon as I’m done? It’s a small lake, very clean and clear. There may be a comment made about me decarbing in it. Lol
I still have grandkids here and another one will be back next week already asking about going out. I hate to disappoint. I’ll probably have them wait on shore while I test run for max wot even though they don’t weigh that much. A little bit in this boat matters.

 

[Douglasdzaster]

I’ve only had it out the one time when I took the grandkids. I’m trying to get everything right before the next lake test but you’re right I’m having to idle to much to do so. I haven’t decarbed yet due to all of the above. Can I do it at home , then change spark plugs or do I need to run wot as soon as I’m done? It’s a small lake, very clean and clear. There may be a comment made about me decarbing in it. Lol
I still have grandkids here and another one will be back next week already asking about going out. I hate to disappoint. I’ll probably have them wait on shore while I test run for max wot even though they don’t weigh that much. A little bit in this boat matters.

I’m on the second carburetor and so far the o rings are messed up on the seats. I remember putting the new ones on when I rebuilt everything. The new seats did not want to go down all the way and I must have messed up the o rings trying to get them flush with the carb body. They’re not even tight now The first one went back together and seated all the way this time and the floats at 15 mm to spec. I had also read it made a difference when installing the needles which way the spring faced. These where backwards.
Everything else is clean so far. I’m still giving them a good going over anyway. Got some 20# test fishing line that goes through all holes.

 

[Douglasdzaster]

I’m on the second carburetor and so far the o rings are messed up on the seats. I remember putting the new ones on when I rebuilt everything. The new seats did not want to go down all the way and I must have messed up the o rings trying to get them flush with the carb body. They’re not even tight now The first one went back together and seated all the way this time and the floats at 15 mm to spec. I had also read it made a difference when installing the needles which way the spring faced. These where backwards.
Everything else is clean so far. I’m still giving them a good going over anyway. Got some 20# test fishing line that goes through all holes.

Number 3 , I had to pick out the o ring. It was clean as well and no water. Replaced the o ring and just like the others it went down to the carb body. I removed each seat after tightening and new o rings were good. I may have had the wrong size the first time. I’ll put the carburetors back on the motor tomorrow. Let me know about decarbing on muffs before I get to the lake.
Your help is appreciated as always.

 

[Faztbullet]

Always lube ring with 2stroke oil

 

[Sea Rider]

Let me know about decarbing on muffs before I get to the lake.
Your help is appreciated as always.

Once all carbs are working right, you can decarbon the motor while running on muffs at home, check post 44 at lower page..

Happy Boating​

 

[Douglasdzaster]

Once all carbs are working right, you can decarbon the motor while running on muffs at home, check post 44 at lower page..

Happy Boating​

I got it all back together and started it up. Still running rough. It would miss and kick , then die. I finally got the pilot screws adjusted and it ran but still rough and rpms changing. I even replaced a needle on number 3 that was sticking closed pretty bad. It had a ring around the tip.
While running it I noticed fuel on top of the water on the ground. realized I had not checked the fuel pump for a leaking diaphragm (at one point I killed it and smoke was coming out of the throat of the bottom carburetor) After adjusting the pilot screw it didn't do it again . I did pull the rope with the hose off and plenty of fuel came out of the pump. I also pulled the spark plugs after running it and they where wet. Could be from running on muffs. But they’re far from black looking and I couldn’t smell gas. They where pretty clean for all the idling it’s been doing. The electrodes had the tan color but it looked like what carbon or oil etc. was being cleaned off. The tale tail stream was kind of weak also but never over heated. I’m just mentioning everything I can think of Incase you see a sign of water getting in the motor or something else seriously wrong. As of now I’ll order a new gasket for the fuel pump so I can pull it and see if it’s leaking in the cylinder. It was running good enough for the decarbing I think. Maybe it’ll help some of the weird stuff it’s doing.
Thanks again for reading my rant and advice.

 

[Sea Rider]

Don't worry Doug, I'd be ranting myself if experiencing same on my motors. Wanted to perform an experiment taching a 3 cylinder Yam 85 individually but my friend is out of town for quite a while. It's very difficult to fine tune a 3 and up cylinder carbs to work spot on and achieve a near perfect idle rpm, luckily for my peace of mind only run 2 cylinder single carbed motors. Would definitely go crazy adjusting 3 carbs at the same time.

If the tach is reading correctly, warm the motor on muffs for say 3 minutes, install the pick up wire on upper ignition coil wire and write down on a piece of paper the idle rpm achieved, remove the pick up wire from the first ignition coil and perform the same for the second and third ignition coils. Compare them to each other, are the 3 idle rpm readings the same ?

If not and with notorious rpm readings differences probably could adjust each pilot screw individually to read even or close to each other ? If works Bingo. BTW this is an experiment. Rough idling could be blamed for too much carbon buildups inside the combustion chamber, carbs badly adjusted or a combo of both situations. Remember that one of the carbs has a larger jet that what the parts manual calls for, if adjusted with same number of out turns as the other two carbs that cylinder theoretically will receive more fuel than the others, if so will need to adjust it to the lean side to compensate.

Tell tale won't peed much if running the motor on muffs due to too much water loss on the ears, deficient house water pressure, a combo of both situations. Motor should peed much better when running at open water. Never seen a motor to overheat at idle on muffs, unless impeller is shot, water hose popped off from muffs and weren't aware of that...

Happy Boating​

 

[Douglasdzaster]

Don't worry Doug, I'd be ranting myself if experiencing same on my motors. Wanted to perform an experiment taching a 3 cylinder Yam 85 individually but my friend is out of town for quite a while. It's very difficult to fine tune a 3 and up cylinder carbs to work spot on and achieve a near perfect idle rpm, luckily for my peace of mind only run 2 cylinder single carbed motors. Would definitely go crazy adjusting 3 carbs at the same time.

If the tach is reading correctly, warm the motor on muffs for say 3 minutes, install the pick up wire on upper ignition coil wire and write down on a piece of paper the idle rpm achieved, remove the pick up wire from the first ignition coil and perform the same for the second and third ignition coils. Compare them to each other, are the 3 idle rpm readings the same ?

If not and with notorious rpm readings differences probably could adjust each pilot screw individually to read even or close to each other ? If works Bingo. BTW this is an experiment. Rough idling could be blamed for too much carbon buildups inside the combustion chamber, carbs badly adjusted or a combo of both situations. Remember that one of the carbs has a larger jet that what the parts manual calls for, if adjusted with same number of out turns as the other two carbs that cylinder theoretically will receive more fuel than the others, if so will need to adjust it to the lean side to compensate.

Tell tale won't peed much if running the motor on muffs due to too much water loss on the ears, deficient house water pressure, a combo of both situations. Motor should peed much better when running at open water. Never seen a motor to overheat at idle on muffs, unless impeller is shot, water hose popped off from muffs and weren't aware of that...

Happy Boating​

I found it a little easier to start with the middle carburetor first. But I got to tell you what happened when I went back out there today.
I decided to test the spark gap with a new tester I got from Amazon. I set the thing for what the specs called maximum at first. Manual says to do this running at 1000 rpms. The first cylinder nothing. Same with the second and third. This isn’t right or the motor wouldn’t be running so I closed the gap to real small to see if the tester worked and still saw no spark. I grabbed my old inline tester you hook to the spark plug wire then to the plug. I laid it down and got in the boat and started it. I had both hands on the motor and just asked my grandson, is it sparking then WAM !!! The tester arched to the motor and lite me up like the lights in Las Vegas! My grandson said he saw all the veins in my neck all at once. I called it a day after that. Amazon’s getting their tester back.

 

[Faztbullet]

You cannot make one cylinder idle different than the others as connected to same crankshaft, if cylinder #1 is at 900 RPM the others will be 900 RPM.

 

[99yam40]

Don't worry Doug, I'd be ranting myself if experiencing same on my motors. Wanted to perform an experiment taching a 3 cylinder Yam 85 individually but my friend is out of town for quite a while. It's very difficult to fine tune a 3 and up cylinder carbs to work spot on and achieve a near perfect idle rpm, luckily for my peace of mind only run 2 cylinder single carbed motors. Would definitely go crazy adjusting 3 carbs at the same time.

If the tach is reading correctly, warm the motor on muffs for say 3 minutes, install the pick up wire on upper ignition coil wire and write down on a piece of paper the idle rpm achieved, remove the pick up wire from the first ignition coil and perform the same for the second and third ignition coils. Compare them to each other, are the 3 idle rpm readings the same ?

If not and with notorious rpm readings differences probably could adjust each pilot screw individually to read even or close to each other ? If works Bingo. BTW this is an experiment. Rough idling could be blamed for too much carbon buildups inside the combustion chamber, carbs badly adjusted or a combo of both situations. Remember that one of the carbs has a larger jet that what the parts manual calls for, if adjusted with same number of out turns as the other two carbs that cylinder theoretically will receive more fuel than the others, if so will need to adjust it to the lean side to compensate.

Tell tale won't peed much if running the motor on muffs due to too much water loss on the ears, deficient house water pressure, a combo of both situations. Motor should peed much better when running at open water. Never seen a motor to overheat at idle on muffs, unless impeller is shot, water hose popped off from muffs and weren't aware of that...

Happy Boating​

the only time a 3 cylinder motor will not be sparking on all 3 cylinders at the same rate is if there something is wrong with the ignition system components. spark is driven my the flywheel turning rate and it does not change speed for the different cylinders
adjusting the individual carb idle circuits has nothing to do with the sparking rate .
monitoring the vacuum to each individual intake while adjusting the pilot screws after syncing the throttle plates is the only true way, but these motors do not have a place to hook up to to monitor their individual vacuum pressures.

my C40 pees a very strong stream at idle on muffs unless the water pump has a problem.
I always use the kit so the wear plate and cup are replaced along with the impellor
But then I run in shallow water a lot so sand and mud is sucked up some times causing wear to the parts

 

[Douglasdzaster]

the only time a 3 cylinder motor will not be sparking on all 3 cylinders at the same rate is if there something is wrong with the ignition system components. spark is driven my the flywheel turning rate and it does not change speed for the different cylinders
adjusting the individual carb idle circuits has nothing to do with the sparking rate .
monitoring the vacuum to each individual intake while adjusting the pilot screws after syncing the throttle plates is the only true way, but these motors do not have a place to hook up to to monitor their individual vacuum pressures.

my C40 pees a very strong stream at idle on muffs unless the water pump has a problem.
I always use the kit so the wear plate and cup are replaced along with the impellor
But then I run in shallow water a lot so sand and mud is sucked up some times causing wear to the parts

Yes sir, I have them adjusted to idle better. Like last time I’ll probably adjust a little more when I get it in the lake with some back pressure on the exhaust.
My concern now is why are the spark plugs cleaner than the last time I pulled them. I’m worried about water going somewhere it’s not supposed to. I was doing a spark test trying to trouble shoot. I also will get out my multimeter and check the coil wires etc. I replaced the water pump with a complete kit less than a year ago but I guess that doesn’t mean it hasn’t been damaged some how. If it doesn’t put out more while in the water I’ll be pulling the lu . I’ve been checking temperature with an ir gun and it’s been in the 140s at the highest.
Thanks for replying to the thread. It’s appreciated

 

[Faztbullet]

Plugs are only clean if: water intrusion which plug tip will surface rust after setting, fuel wash from flooding carb/s or excessive lean at WOT.

 

[Sea Rider]

Need to perform the CRC decarbon procedure, I'm sure that motor has tons of carbon builups on the piston rings, exhaust and combustion chambers, will idle much better after a long wot run an if stealing the combo for say 10-15 minutes. Can re adjust idle screws if in need. FB, explain how can a motor run lean at wot with impeccable clean, well adjusted carbs when all the high speed jets are non adjustable fixed jets ? A motor can run lean at idle, but at wot ?

Happy Boating​

 

[99yam40]

Faz was only giving reasons for clean plugs

but then people play with jetting all the time changing things and some jets/passages can get partially restricted.
someone saying the carbs are clean does not always mean that is true