88 Marathon timing tips

Buggy_Doug · 05-04-2013, 04:26 PM

Ok. I wasnt lent down a path yet on this Marathon. On a new comp tester I have 120 psi. woo-hoo. Ideas. Could air gap do this. As I have said I put a light on it and see those marks are very forgiving. Timing doesnt move a whole heck of a lot if your not quite on. Ideas? I may pull the carb to check on the gassy exhaust. Maybe pull apart the fuel pump to be sure. On the flip side, will polarity of the wires on the pulsar effect forward reverse speed.? As for a governor. Its missing. Frankly I dont see how they work as I have yet to find a diagram of this one. I just have a knurled stub on a lever with a cable to the throttle arm. It stops it at a full position or there abouts.

Buggy_Doug · 05-04-2013, 04:43 PM

Oh. It sounds notably faster in reverse. I have some clutch bushing wear that I suppose could be a problem but the engine is peppier in reverse than forward.

Buggy_Doug · 05-04-2013, 06:34 PM

Ive put the marks back to center. When it started it ran great, then loaded up and slowed so I checked the fuel pump ok and the Carb. It has so much weare on the butterfly at the shaft its amaging. The float as well looks a little dicey in that the tang is on an angle to set it level to the bowl gasket. I need parts I think.

racin161 · 05-04-2013, 07:29 PM

Yep sounds like it. With a worn throttle shaft you have a major air leak. It sounds like a new carb is in the future as parts will cost about 2/3 what a new one would and you still have a worn throttle shaft. Are you sure the choke is not closing on you? Governor no problem most of us remove them. Yes polarity does make a difference on the pulser blue wire to A terminal an red to B from the igniter.

LOU

BrewCityMusic · 05-04-2013, 08:42 PM

And not to second Lou's opinion yet AGAIN, but I second that - although I will throw in that there really isn't (at least in MY experience) a difference in polarity really, one way it works one way it doesn't (literally, 2 black wires and a unidirectional plug that says "Reverse and Neccessary" wouldn't have been entirely out of order in this case)

racin161 · 05-05-2013, 11:40 AM

Brew & Buggy these were per instructions from ezgo {issue date 1985} and the recommended wire connection at the pulser with stock ignition. Agreed with hei conversion at times they will be reversed.

Just saying

LOU

Buggy_Doug · 05-24-2013, 06:18 PM

Got my carb, finally. It had no low speed. I opened it up to find the carb is slightly different from the original Mikuni. This one too says Mikuni but I have my doubts that its a cheap copy. The atomizer well was only in by 2 threads blocking the passage for the idle circuit. Some looking found the depth of the hole shorter. Bad copy. I had to index the position it stops at and cut a releif slot for the start of the passage but it hasnt helped much. Any ideas. The old carb had too much wear on shafts and pivot holes but did idle on this engine. This one I have to choke it every time to start. I reset the starter switch to idle it down but its starves and dies of fuel. Choke restart to get going otherwise it cranks and cranks. . . . Im going to look at the idle further but ideas anyone.

Buggy_Doug · 05-24-2013, 06:24 PM

Oh. It revs good both ways now!

Buggy_Doug · 05-25-2013, 08:17 PM

I have to take back the runs OK both directions. Only did that for a moment until it cleared. I re-cleaned the new carb and had something quite solid blow out of the idle passage. It runs and idles on it but I still had the same problem of it being a dog in forward and peppy in reverse.

Well boys! I have found the problem. I had done a compression test with 120 psi but hadn't thought about doing it both ways. So I did and with the reed block out as well. Now this is the interesting part. In forward it will get to 120 but hesitates a bit around 90 psi. In reverse it goes right up smoothly. If you rotate the flywheel by hand you get a bounce turning reverse and leaking going forwards. I pulled the engine and found **** near a quarter of an inch of end gap on the top ring.

Its just order parts and this belated Mothers Day present will have to wait a little longer to drive a little old lady (Mon) around the property.

heres a couple of pics.

Buggy_Doug · 06-21-2013, 06:53 PM

I have some other issues yet to deal with but I'd like to ask. Where on Gods green earth did some knob come up with a gas ratio of over 100:1

Try this link
http://www.ultralightnews.ca/fujirobinmanual/

Yah its a plane.

05-04-2013, 04:26 PM	#11
Buggy_Doug Not Yet Wild Join Date: May 2013 Posts: 11	Re: 88 Marathon timing tips Ok. I wasnt lent down a path yet on this Marathon. On a new comp tester I have 120 psi. woo-hoo. Ideas. Could air gap do this. As I have said I put a light on it and see those marks are very forgiving. Timing doesnt move a whole heck of a lot if your not quite on. Ideas? I may pull the carb to check on the gassy exhaust. Maybe pull apart the fuel pump to be sure. On the flip side, will polarity of the wires on the pulsar effect forward reverse speed.? As for a governor. Its missing. Frankly I dont see how they work as I have yet to find a diagram of this one. I just have a knurled stub on a lever with a cable to the throttle arm. It stops it at a full position or there abouts.
Buggy_Doug Not Yet Wild Join Date: May 2013 Posts: 11

05-04-2013, 04:43 PM	#12
Buggy_Doug Not Yet Wild Join Date: May 2013 Posts: 11	Re: 88 Marathon timing tips Oh. It sounds notably faster in reverse. I have some clutch bushing wear that I suppose could be a problem but the engine is peppier in reverse than forward.
Buggy_Doug Not Yet Wild Join Date: May 2013 Posts: 11

05-04-2013, 06:34 PM	#13
Buggy_Doug Not Yet Wild Join Date: May 2013 Posts: 11	Re: 88 Marathon timing tips Ive put the marks back to center. When it started it ran great, then loaded up and slowed so I checked the fuel pump ok and the Carb. It has so much weare on the butterfly at the shaft its amaging. The float as well looks a little dicey in that the tang is on an angle to set it level to the bowl gasket. I need parts I think.
Buggy_Doug Not Yet Wild Join Date: May 2013 Posts: 11

05-04-2013, 07:29 PM	#14
racin161 Gone Wild Join Date: Feb 2011 Posts: 1,515	Re: 88 Marathon timing tips Yep sounds like it. With a worn throttle shaft you have a major air leak. It sounds like a new carb is in the future as parts will cost about 2/3 what a new one would and you still have a worn throttle shaft. Are you sure the choke is not closing on you? Governor no problem most of us remove them. Yes polarity does make a difference on the pulser blue wire to A terminal an red to B from the igniter. LOU
racin161 Gone Wild Join Date: Feb 2011 Posts: 1,515

05-04-2013, 08:42 PM	#15
BrewCityMusic Hammer Down !!!! Join Date: Jun 2010 Location: Lake Geneva, WI Posts: 2,681	Re: 88 Marathon timing tips And not to second Lou's opinion yet AGAIN, but I second that - although I will throw in that there really isn't (at least in MY experience) a difference in polarity really, one way it works one way it doesn't (literally, 2 black wires and a unidirectional plug that says "Reverse and Neccessary" wouldn't have been entirely out of order in this case)

Today
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05-05-2013, 11:40 AM	#16
racin161 Gone Wild Join Date: Feb 2011 Posts: 1,515	Re: 88 Marathon timing tips Brew & Buggy these were per instructions from ezgo {issue date 1985} and the recommended wire connection at the pulser with stock ignition. Agreed with hei conversion at times they will be reversed. Just saying LOU
racin161 Gone Wild Join Date: Feb 2011 Posts: 1,515

05-24-2013, 06:18 PM	#17
Buggy_Doug Not Yet Wild Join Date: May 2013 Posts: 11	Re: 88 Marathon timing tips Got my carb, finally. It had no low speed. I opened it up to find the carb is slightly different from the original Mikuni. This one too says Mikuni but I have my doubts that its a cheap copy. The atomizer well was only in by 2 threads blocking the passage for the idle circuit. Some looking found the depth of the hole shorter. Bad copy. I had to index the position it stops at and cut a releif slot for the start of the passage but it hasnt helped much. Any ideas. The old carb had too much wear on shafts and pivot holes but did idle on this engine. This one I have to choke it every time to start. I reset the starter switch to idle it down but its starves and dies of fuel. Choke restart to get going otherwise it cranks and cranks. . . . Im going to look at the idle further but ideas anyone.
Buggy_Doug Not Yet Wild Join Date: May 2013 Posts: 11

05-24-2013, 06:24 PM	#18
Buggy_Doug Not Yet Wild Join Date: May 2013 Posts: 11	Re: 88 Marathon timing tips Oh. It revs good both ways now!
Buggy_Doug Not Yet Wild Join Date: May 2013 Posts: 11

06-21-2013, 06:53 PM	#20
Buggy_Doug Not Yet Wild Join Date: May 2013 Posts: 11	Re: 88 Marathon timing tips I have some other issues yet to deal with but I'd like to ask. Where on Gods green earth did some knob come up with a gas ratio of over 100:1 Try this link http://www.ultralightnews.ca/fujirobinmanual/ Yah its a plane.
Buggy_Doug Not Yet Wild Join Date: May 2013 Posts: 11

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