1975 25 HP Timing

[Richard911]

Where is the shaft supposed to be when I gap point #1 to .020?
When in neutral and wot my roller is lined up with the first mark on the armature plate. The book says its supposed to be between the two marks. Is this an issue?

 

[steelespike]

Re: 1975 25 HP Timing

The flywheel key needs to be lined up with the point rubbing block.
There is a timing fixture that is used to get the points opening exactly 180 degrees apart.I doubt many use one.
If I remember right as you advance the throttle the roller needs to be between the marks just as it contacts the armature plate cam.
not at wot.
There is a wot timing procedure as well.

 

[Richard911]

Re: 1975 25 HP Timing

Thanks. When syncing the carb, I can't get the roller to line up between the marks unless I'm in gear.
What position should the throttle be in when I set the points?

 

[OptsyEagle]

Re: 1975 25 HP Timing

The throttle can be in any position when setting the points. I usually check it at a couple of positions just to see if my armature plate is wobbling or warped. Luckily it measures the same at all the throttle positions because I probably couldn't do much about it if it didn't.

Having the motor in gear should not make any difference in syncing up the carb. Are you saying that the roller hits the throttle cam in one spot, when in neutral, and it hits at another spot on the throttle cam, when it is in gear?

 

[Richard911]

Re: 1975 25 HP Timing

Thanks for that. No, I'm saying that when you advance the handle as far as you can in neutral, the roller is in line with the first mark on armature plate. To move the roller forward so that it is in between the marks, you must put it in gear.

 

[Richard911]

Re: 1975 25 HP Timing

She's not idling is the issue I'm having but she also hasn't run in twenty years either.

 

[OptsyEagle]

Re: 1975 25 HP Timing

I am not personally familiar with the 25Hp but I have set a few carbs to the throttle cam. When setting the carb you want the roller of the carb to hit the throttle cam (which is on the armature plate) at a point marked on the cam. This is the point that the cam just starts to push on the roller which opens up the carb butterfly. On all the motors I have ever owned, the roller hits the cam before you hit the neutral stop on the motor. If not the carb would not be open at all during start up and I would think it would need a little more gas, but perhaps the 25Hp operates a little different.

All of the above is simply to ensure that the spark timing is advanced properly throughout all the RPM ranges of the motor, including idle. So it can be important to good idle, however, bad idle could also be a dirty carb. I would imagine after 20 years of sitting that it could probably use a cleaning with a rebuild kit. Also, the points would definitely need to be filed and cleaned very well, or replaced. Then set the shaft to the "set" spot and ensure they have a 0.020" gap (0.022" if brand new) at that spot.

 

[dkonrai]

Re: 1975 25 HP Timing

check your coils as well. i have a 72 20hp. i have some idle issues too, but it runs ok in the water vs running it in a tank.
compression test, clean the carb, coils, points, condenser.
dino

 

[Richard911]

Re: 1975 25 HP Timing

The devil is always in the details. I was lining the roller up with the two marks on armature not and not the two marks on the THROTTLE CAM.

 

[Richard911]

Re: 1975 25 HP Timing

I also just adjusted the points while at the "set" mark. The motor is running the best it has yet but still won't idle with the butterfly in the closed position. I'm going to take apart the carb, again.

 

[Richard911]

Re: 1975 25 HP Timing

I've thoroughly cleaned and rebuilt the carb. I've also replaced the points, condenser, and stator coil. I now have it idling with the butterfly valve closed. However as soon as I back the throttle all the way down, it stalls.

 

[OptsyEagle]

Re: 1975 25 HP Timing

On my motors of that vintage, they will all shut down, at some point, when I reduce the throttle. If the roller is off the cam and she is still idling and not shaking like crazy, I would say she is running pretty good.

 

[Richard911]

Re: 1975 25 HP Timing

It will run but only when just barely off the cam. I think I hear a knock occasionally also.

 

[tjhamms]

Re: 1975 25 HP Timing

Check your linkage again. Make sure you moved the throttle linkage to set the roller to make contact with the cam.You want the roller to be in the center of the mark. At this point the butterfly should start to open. If this checks out, you may have to adjust the slow speed needle to get it to idle properly.

 

[tjhamms]

Re: 1975 25 HP Timing

Sorry one more thing, make sure you are not confusing the butterfly with the choke.

 

[OptsyEagle]

Re: 1975 25 HP Timing

I agree with tj above. Ensure your carb is synced in the right spot. Obviously, if the carb butterfly is shut, the only thing that is happening as you reduce the throttle, is you are moving the spark timing further past TDC, until eventually it is so far past TDC, the motor dies. So if this carb sync is already set too far past (roller hitting the throttle cam "before" the mark), then this point will come sooner then it should, as you reduce throttle.

Also, when it has warmed up you want to ensure that your slow speed carb adjust is set right. You could try adjusting it a quarter turn counter-clockwise and see if that helps.

The last thing I would check is if both cylinders are indeed firing and are strong enough to run the motor. These motors will run incredably well with only one cylinder working, to the point that having a failed cylinder is almost unnoticable, when running in a barrel. What I usually will do, after I have tuned up my motor, is fire it up, warm it up and at a faster idle, I will take a pair of insulated plyers and pull off one spark plug boot at a time. The motor should keep running when either boot is removed. If it dies, then you know that the other cylinder was either not firing or was very weak. If this does happen, reply back and we can give you some tests to identify why only one cylinder is working, but in any event, this is a good check to do.

 

[steelespike]

Re: 1975 25 HP Timing

As you back down the throttle you further retard the spark. Makes sense it would stall.
As I understand it the throttle follower should be just touching when between the marks on the armature plate cam.
Its possible that it needs to be in forward to set it.

 

[nwcove]

Re: 1975 25 HP Timing

It will run but only when just barely off the cam. I think I hear a knock occasionally also.

you sure its a knock? or maybe just a mild backfire/shake? if so you may need to try some different settings on the ls needle. ( if i remember correctly, the ls dial isnt directly connected to the needle, so you may have to temporarily remove that linkage .)

 

[Richard911]

Re: 1975 25 HP Timing

I pulled each plug boot out separately (cool trick) and the motor continued to run.
I double checked the linkage and can't imagine getting the carb synced any closer than it is.
I have tried adjusting the low speed needle throughout this entire process and believe it is set at the optimum place because if I move either in or out the motor doesn't run as well.

This motor is definitely old but also definitely still not running right. It pulls and starts very easily when the roller is lined up with the marks but will not start or idle if the throttle is turned down below that. The armature plate rotates about 2 inches when I turn the throttle handle down from the two marks to the stop position. That means that the butterfly valve is closed for the entire 2 inches the timing is retarding.

 

[Richard911]

Re: 1975 25 HP Timing

I ran it in the canal yesterday and while under a load it performed perfectly. I didn't hear the knock again either which is good. Unfortunately it still stalls when you turn the throttle down. I also noticed that my head gasket was leaking water a little. Would poor compression cause these issues?