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Discussion Starter #1
Having read all I can find on this problem it seems quite common. The descriptions given are always the same, Heat makes the sensor act up at first then finally it goes open circuit and the engine won't start. I tested the sensor by first putting the ohms meter on it, 385 ohms,held it in my closed hand with meter probes in place and watched the ohms rise until it went open circuit.Put it in the fridge for 10 mins. it came back again once or twice but now its totally open circuit.Red light Codes in the computer of the LTD steady "W" & flashing "0" & "3" which is exactly what the book says to look for,Crank Pulse Sensor. For the record since there has been some confusion in the past about pulse sensors this is the one inside the Timing Belt cover taking a trigger pulse off the Crank with a wire exiting the top of the Timing belt cover,part #30300-MG9-951 (original part) These sensors are all but non existent now anywhere in the world. There is a couple of ways to fix this, there is a company that rebuilds them.. or part # 30300-MN5-003 which is a pulse generator from a GL1500 which is more durable. Its a dual sensor so one can be a spare on the shelf, however it takes some modification to install because the mounting tabs are a bit different.I have one here which I'm going to install according to previous info given here. LTD & SEI owners beware its not a matter of "IF" this sensor goes its "WHEN" because it "WILL" fail eventually, my 85 LTD has 95k miles,its down until this is fixed,my sons LTD went around the same mileage a few years ago.
 

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The Irish Crew
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Can you post pictures of the mod and install Sparky? I think a lot of owners will be interested in this.
 

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I think it's been documented that the carb'd 1200 PG's will work without modification, by only using one pg.
 

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Discussion Starter #4
1985 GL1200 LTD Crank Pulse Generator "FIXED"

My 85 LTD had been acting up,sometimes would'nt start when it was hot. It got worse over the summer until on a ride one day it would'nt start at all til it cooled down for an hour,then it died completely. Computer code steady "W" Flashing "0" & "3" Crank Pulse Generator part # 30300-MG9-951. I phoned around and surfed the internet for another one...well they are no longer available. I read a post by "Oregonwinger" dated 2008 where he suggested using a sensor from a GL1500 part #30300-MN5-003 so I ordered one and had it the next day. The two mounting studs inside the timing belt casing needed to be cut back 8 mm to accomodate the new sensor. The casing has two sets of mounting studs one above the trigger pulley and one below,the original sensor used the lower two mounting studs, I cut the upper two mounting studs the 8 mm since they were exactly in the correct place for the sensor (the 1200 carbed models have two pulse sensors whereas the EFI has one pulse sensor leaving the second two mounts unused. I thought if anything went wrong I'd still have the original lower mounts intact. The reason for cutting the mounting studs is so the pickup point of the sensor will line up with the trigger points on the pulley since the old and new sensors mount a bit differently. I set the air gap at 0.7 mm hit the key for a second to see if it fired up..it did and I shut it off of coarse since no rad or coolant.Wired it permanent put it back together took a test run and its fixed. Thanks to my son his knowlege of Motorcycles and for this website and some very important info Oregonwinger shared back in 2008. This upgrade is a good one and the new sensor is more durable,not so heat sensitive.;)
 

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Discussion Starter #5
old sensor 2.jpg

new sensor 2.jpg Here is the old crank pulse generator sensor(top photo)before it was taken out from underneath the trigger pulse pulley and the new crank pulse generator sensor (bottom photo) above the trigger pulse sensor after the install. Notice there is two sets of sensor mounts one below and one above the trigger pulse pulley.
The gl1200 Carbed models have 2 pulse sensors thus the two mounts. The EFIs (85 LTD & 86 SEI) have one crank pulse sensor so the extra mount is'nt used. I used this to an advantage by modifiying the upper mounting studs (cutting 8 mm off them)and leaving the lower mounts intact just in case. The upper and lower mounts are spaced the same from the trigger pulse pulley so either mounting point works. The air gap for the sensor is 0.4-0.9 mm or (0.016-0.035 in) using a feeler gauge. I set mine 0.7 mm
During a road test, no dead spots, smooth steady power right through the power band,idles smooth,starts in an instant hot or cold. All in all a good upgrade and the sensor is more durable than the original, its a bit bigger so I beleive they wrapped the coil in more outer protective material to prevent its sensitivity to heat which was the problem in the first place.
 

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Very interesting.

I wonder if this would work on a
83' GL1100 or
84'GL1200

Since they have the PG's in the back of the engine.

I have a 83' GL1100 and a 84' GL1200 is why I ask.
 

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Question to the experts: Are the 1200's carb and fi both waste spark systems? I would like to dump the exhaust spark. Reading that the FI model has one PG, makes me wonder.
 

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Question to the experts: Are the 1200's carb and fi both waste spark systems? I would like to dump the exhaust spark. Reading that the FI model has one PG, makes me wonder.
Your reading is incomplete. the fuel injected models have three pulse generators one on the front of the crankshaft and two on the rear of the right camshaft.

Changing to four coils each firing only when needed would require re-engineering the complete system and for what advantage?
 

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Thanks, Ken. Is the one on the front just for the injection, then? Two on the cam for ignition? My reading is very incomplete. Getting rid of the waste spark might help smooth the idle.
 

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Junior Grue
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There are millions of engines using the wasted spark method that idle smoothly.
If you have an idle problem I'd look elsewhere.
 

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Thanks, Ken. Is the one on the front just for the injection, then? Two on the cam for ignition? My reading is very incomplete. Getting rid of the waste spark might help smooth the idle.
Won't make a bit of difference since the wasted spark is near the top of the exhaust stroke, no burnable mixture in the cylinder at that time.

The non EFI four cylinder 'Wings have had problems with failing pulser coils as well. The normal symptom is the engine shutting off when it gets warm and not restarting until it cools down. One of the tests is similar to what Sparky mentioned. I've used a heat gun and watched the resistance of the coil as it heated up as a diagnostic. I don't think I've seen one that would open up from the heat of a hand, it seemed to take a bit more heating than that on the two bikes I worked on in my shop with pulser failure.
 

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hey sparky, you mentioned that the pulse sensor for a 1500 would fit, but my question is....did you have to cut one of the pulse sensors off making it a single sensor. the reason I ask this is I have a chance to pick up an 86 GL1200 SEi that has a bad crank sensor for $500 bucks. with the way you did yours, would it work the same if I did it to mine if I couldn't find an OEM 1200 crank sensor?


stuart, a.k.a. roadwanderer2.
 

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hey sparky, you mentioned that the pulse sensor for a 1500 would fit, but my question is....did you have to cut one of the pulse sensors off making it a single sensor. the reason I ask this is I have a chance to pick up an 86 GL1200 SEi that has a bad crank sensor for $500 bucks. with the way you did yours, would it work the same if I did it to mine if I couldn't find an OEM 1200 crank sensor?


stuart, a.k.a. roadwanderer2.
Do what I did buy the pulse generators for a 1200 carbed . They will fit like the orginal one for the FIs you just have to change the plug end . I just pulled out the wires and and just used the two you'll need and tape up the other two . I install both top and bottom just like the carbeds . Only one will work and the other will just be there . If it goes bad you will only have to switch the wires around on the plug instead having to romove the rad and drain coolant . I did this on my newly aqired LTD. Runs like a top now
 

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thank you rightwinger. i appreciate your response to my question. when i get this bike today i'll start making up a list of what has to be done to it. here are a few pics of it as it sits right now.

stuart.
 

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let the games begin!!!

well a friend of mine and i went to pick up my new motorcycle yesterday. it took me and 3 other guys to roll it onto the trailer. this bike is HEAVY. its got some weight to it i can tell you that much lol. of course when i got it home the first thing i had to do was purchase a new battery. i had to leave it on my battery tender all night to charge it up before i can connect it to the bike, so i don't know if its fully charged yet. next thing to work on after i get it started up will be the rear brakes. for some reason the rear brake it locked up. i suppose i'll have to rebuild the brake caliper, then get new timing belts because when i spoke to the old owner on the phone, he could not tell me when they were replaced before. i'll keep ya's posted on my progress. here is a pic of what my new wing looks like right now as it sits.
stuart.
 

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ok, new battery in, had to put some fuel in the tank because it was bone dry, turn the key and all the lights and gauges lit up, and when i went to try to start it, it cranked but didn't fire up. the PO told me that when he put the bike on his diagnostic machine, it read bad crank sensor, now my question is this......can the bad crank sensor keep the bike from starting up?

stuart.
 

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so im looking at the crank sensor, following the wires looking for where its supposed to be connected, and its not even connected to anything. does anyone know where this thing is supposed to be connected at? i cant find the other end of this connector. as far as i can see, the wire runs thru the front engine case via a rubber grommet and up the left side and into an area thats in the left side of the fairing and connects somewhere up inside the fairing wiring but i cant find the other end of the connector.

stuart.
 
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