1991 Suzuki DT 85 Intermittant Spark

rino · Mar 31, 2004

I have a '91 DT 85 that has intermittant spark confirmed with a timing light. We bought it a few weeks ago; replaced and gapped plugs to .35, rebuilt the starter, put a new battery, found the kill switch had to be pushed in with a screwdriver (I will replace it) and it ran okay on muffs for a minute but had low water output so we replaced the impeller (thanks to the old posts this board I was able to do this with no problems). Try it again last week and all I got was a spark boom (like a backfire), then nothing. Open the control box, disconnect and reconnect all the connections (clean), the kill switch measures 0 ohms when pressed, infinity when let go. Disconnect and reconnect all the linkages on the motor, try again. About every 3rd try I get a spark right when I turn the key, but never a spark as the flywheel is turning. Disconnect the kill switch in the control box and no difference. Check the neutral interlock in the control box, no problem. I started checking coil resistance but my clymer manual says to check between the two colored wires on the coil; my coils only have one colored wire, two bolts to ground, and a spark plug wire built-in. Measured resistance between spark plug connector and bolt holes and found all three consistant readings (maybe 10K ohms) I have only the basdic multimeter, not a peak-reading voltmeter so I don't know where to turn now for troubleshooting. Where can I get a peak-reading voltmeter (I heard the Stevens CD-77 mentioned but couldn't find one online). Disconnected the rectifier with no difference. The first bad sign from the stator is an unconnected red wire with yellow stripe. All other connections as by the book. One more bad sign is the clymer says I should have three pulser coils, I have two (I read here two are shared between cylinders). There was one fuse in the motor which tested good. The gearbox is in neutral with the shift linkage is disconnected at the engine. The woodruff key is fine and all magnets on the flywheel have been tighened. Other than temporaily disconnecting the kill switch in the control box I did not make any other wiring changes and all the colors match up. I reconnected the kill switch and no change; I might get spark the second I turn the key, but never while the flywheel rotates. The flywheel turns fairly quickly when the starter is engaged and it does not drag. There is an inner set of coils on a base that turns if you adjust the linkage on the starboard side. Is this the low-speed timing adjustment? Is there a better way to test the stator and coils? Should I get the best resistance assume using the resistance listed for other units and com Does the the Seloc manual provide resistance info for a '19 DT85? Is the SelocOnline.com CD as complete as the paper book version? Thanks for help in advance.

rodbolt · Mar 31, 2004

Re: 1991 Suzuki DT 85 Intermittant Spark

hello on this engine you should have 3 pulsar coils ( trigger coils) and one CDI condenser charging coil. the resistance on the pulser coils r/b to ground160-240 ohms w/b to ground and r/w to ground are the same. condenser charge coil is green to black with a red tube 170-250 ohms. how and when did this problem start? the CDI unit is self powered I cant see where just turning thge key will make it spark or not unless something is wired way wrong. tell me how the problem started ie were ya just cruising along and blam no run or was it running and then a maint action was performed and now it does not run.I would test all the cdi grounds. white wires are hot if the battery is hooked up green/red tracer wires are hot when the key is on black wire is ground and green wires are kill circuits.look for the suzuki electrical manual 99514-03930-o1E. has a lot of killer info. also the kill switch descripton is backwards, should be open circuit when pressed and closed when released. this system grounds the cdi to shut down. dissconnedt it and try again. if you now have spark your fine. the stop switch may be the magnetic cap type and it wont work properly by just pushing it with a screw driver. good luck and keep posting

rino · Apr 2, 2004

Re: 1991 Suzuki DT 85 Intermittant Spark

I appreciate the response. There is an outer core of orange coated coils that are stationary close to the flywheel, then there is a set of two small black coils on a rotating surface inside that closer to the shaft. There is a small connector that has three wires (r/b, black, and r/w) that goes to the inner coils. Testing the resistance on these coils with the CDI disconnected and probing the coil end of the wires: no wires show continuity with the engine ground (not even the black one). One combination like r/b and black shows about 125 ohms, all other combinations are infinity (even r/w to black). I will verify the colors and readings later (I left my notes at home). I disconnected the green wire at the CDI with no change. Where is the condenser coil? Is it in the outer stationary ring? I found yellow, white, and other colored wires but no green to black with a red tube I still have a red with yellow stripe disconnected (looks like it goes to the outer ring of coils). We never ran the boat for very long. We bought the boat about a month ago; gave it fresh gas, a new battery, new plugs; fired it up and had a weak starter. Rebuilt the starter and tried it; it started and ran fine at idle but no water. Replaced the impeller and drained and filled lower unit oil. Put the lower unit back on and tried it; it ran okay and water was coming out the tell tale. Pulled off the carb plate and sprayed some carb cleaner in the carb, tried to start it again and I just got a backfire. Since then the only time it gets spark is right when the starter engages; as the starter turns it never gets a spark. The starter turns fairly quick and I keep the battery charged. I disconnected and reconnected all the wires including testing the neutral interlock in the control box. everything checks out per the Clymer manual. All grounds I found were removed, cleaned, and reconnected: no change. I checked the blue wire (thermal switch?) infinite resistance to ground (I haven't confirmed if this normal). I could not find the Suzuki electrical manual 99514-03930-o1E online; Do you know where I can get ahold of one? I have a Clymer manual and a Seloc manual on the way. How can I test the ignition coils? I have only one colored wire, two bolts to the engine (ground) and a spark plug output. Is the primary resistance between colored wire and ground screws, then secondary resistance is between plug lead and ground screws? Thanks for the help.

rino · Apr 2, 2004

Re: 1991 Suzuki DT 85 Intermittant Spark

Update: I removed the stator and timing assembly and spark coils to test them more indepth. The stator physically looks okay but the readings look questionable. On the three wire connector Black to Red/white show 123 ohms, red/black shows infinity to all wires. Could the red/black be an open circuit? The crimp connectors and connections at the connector look good; continuity on the meter. Remaining stator wires: Yellow to Red/Yellow and solid red any combination) are 0.3 ohms. Infinite resistance from yellow to black or red/white or red/black. The timing assembly the inner set of coils that turn with the throttle) has two coils and 4 wires. Yellow/Red to Green is 340 ohms, pink to white/red is 340 ohms; could this be a timing base from the wrong model year? I removed the spark coils to test them. To confirm my previous mistake, the stator resistances were 0.3 ohms which apparently is a a valid resistance. I tested the spark plug coils again after removing them from the engine. The Clymer manual says the primary should be 0.2 to 0.3 ohms, secondary should be 1800-2800 + 10K ohms spark plug cap Does this mean my primary on coil 1 is too high (3.4 ohms)? I'll try cleaning it to see if that makes a difference. Spark plug coil number 1: primary too high? Orange wire to either bolt hole for ground 3.4 ohms between each ground hole 0.3 ohms (the regular value) Orange wire to spark plug lead 2.45 K ohms Spark plug lead to either ground 2.45 K Sounds like primary is 3.4 ohms, secondary is 2.45 K? Spark plug Coil number 2: low? Light blue wire to either ground 0.5 ohms Between each ground hole 0.3 ohms Plug lead to light blue wire 2.4 K ohms, plug lead to each ground screw 2.4K ohms. Spark plug coil 3: weird? Gray wire to top ground screw hole 10 ohms, gray wire to bottom ground screw hole 0.4 ohms between each ground hole 2.8 ohms Spark plug lead to gray wire 2.50 K ohms Spark plug lead to either ground screw hole: 2.5 K ohms Back to verify the stator: 3-wire connector black to red/white 125 ohms black to black/red infinity black/red to red/white infinity yellow to red/yellow is 0.6 ohms yellow to red is 0.6 ohms red/yellow to red 0.3 ohms There are two coils on the timing base, are these pulser coils? I get 340 ohms for both pink to red/white and light green to yellow/red From the Clymer manual it looks like this could have pulser coils from the wrong year or they're out of spec for my '91 engine. Could any of these issues be enough to give me an intermittent spark? Coil number 1 has 3.4 ohms instead of 0.3 (I'll try cleaning the terminal and retesting) The black/red lead in the stator not showing resistance to anything Pulser coils at 340 like an earlier year model? Today I removed all the old wiring and anything that might be causing a kill condition, cleaned and re-connected all grounds and other wire connections. Looking at the pics in the Clymer manual, my ignition coils and pulser coils look like they match a '85 to '87, not a '91 like I was told I have based on my serial number. Could they have mixed the wrong parts and it only ran before because of some miracle of coincidence? Any ideas?

rodbolt · Apr 4, 2004

Re: 1991 Suzuki DT 85 Intermittant Spark

hello if you have a movable stator you dont have a 91 model I will try tomorrow to assist more. I dont have the books out right now. good luck and hold what ya got and I will attempt to help.

rino · Apr 4, 2004

Re: 1991 Suzuki DT 85 Intermittant Spark

Thanks again (and again) Rodbolt, In case it helps, I took pictures and posted them to http://www.hyperfrogs.com/pictures/suzuki The stator does not move, but the "timing base" or what I believe is the pulser coils moves with the throttle linkage. I disconnected all the unknown wires and reconnected grounds; still no good. Still wondering about the stator and red/black wire. The coil on the stator where the red/black looks like it goes is a tiny bit loose (you can wiggle it enough to make a clicking sound. It looks like my pulser coil resistance and coil configuration would be a better match for a pre-1985-1987 DT85; no gear counter, no throttle position sensor. All the wire colors match from the CDI to all the parts so I would expect either the engine itself is an earlier model or it has entirely older-model parts. Maybe the pictures including close-ups of model numbers might help at the link above. I'm playing with the stator and one of the two big coils is a tiny bit loose and it looks like it might be holding the red/black and red/yellow wires. Maybe the "backfire" I heard was a the flywheel smacking this coil which resolted in opening the coil circuit? If that's the case is there somewhere that repairs stator coils or somewhere I might find a used one? I heard a new stator might be $300 or more which is what I paid for the boat. Thanks in advance.

rodbolt · Apr 5, 2004

Re: 1991 Suzuki DT 85 Intermittant Spark

HELLO its definatly older than 87. You also need to ditch the blue crimp connectors and try to solder the wires.I will look to see how much old stuff info I can find. but none of the coils should be loose. the charge coils are the 2 big black ones on the stator the pulsar coils are the 2 small ones on the trigger ring. the smaller coils on the stator are for battery charging. good luck and keep posting

jim dozier · Apr 5, 2004

Re: 1991 Suzuki DT 85 Intermittant Spark

Based on the serial number which I make out to be 8501-104890 and using the parts chart on www.brownspoint.com it appears that its a 1981 or a 1990. You have been very thorough and organized throughout this ignition investigation but I have to ask- How did you verify that there was no spark? Did you use a spark tester or something similar or do you mean the engine will not "fire" when cranked.

rino · Apr 5, 2004

Re: 1991 Suzuki DT 85 Intermittant Spark

Brown's Point is invaluable! I just found I'm missing a flywheel locknut not even shown in the Clymer manual and I figured out my own engine year which the dealer did not. Now I'm 99% sure I have an '81; the parts I have look just like the diagram. It's unfortunate that my manual only goes back to '85; better to find out this way than to buy a new stator and other parts and find out the hard way. I was using a timing light as a spark tester, then the spark plug connected to a ground bolt to test it 'live'.

rino · Apr 6, 2004

Re: 1991 Suzuki DT 85 Intermittant Spark

Now I'm 95% sure my sttator has an open winding on the red/black to black circuit; and the coil it goes to is a bit loose. Is there anywhere that can repair a stator for under $100? The Suzuki dealer said a replacement is $314. If I can get it fixed for shipping plus $50 or even $100 that would be really good. Any used parts would be great also. The stator assembly is the same for a few different models; any idea where to pick up a used one?

jim dozier · Apr 7, 2004

Re: 1991 Suzuki DT 85 Intermittant Spark

Check Ebay, from time to time you can find parts for that motor listed there.

rino · May 17, 2004

Re: 1991 Suzuki DT 85 Intermittant Spark

I saw a listing on eBay, missed the auction because of vacation, contacted the buyer directly and viola.... I have a used stator swapped out and my spark has been restored!!! The engine idles a little rough; new plugs installed at 35 gap, 50:1 fresh gas (also oil in the oil tank), consistant spark confirmed via timing light on all three cylinders. Try unplugging to test fire on all 3 cylinders: uplug top cylinder and it pops a bit more, unplug cylinder two and it speeds up!, unplug cylinder 3 and no difference. TellTale spits out a good flow of water. Take plugs out after 4-5 minutes they're equally oiled. I have an upper oil seal (the piece the stator screws into) to replace; the old one was missing the rubber ring and the new one has too small a ring to fit around the crankshaft. Fiddling around with the Clymer manual isn't helping to find how to get the rubber around the crankshaft without breaking it. After the oil seal is replaced and I confirm the oil injector is working I'll revert to regular gas and use oil injection. Could the extra oil be enough to run crappy? If I rev up in neutral it sounds good but dies if quickly turned down to idle. Could my leaky oil seal also cause bad performance? I lowered the gap to .25 with no difference. It's a 1981 DT 85; just got it running on muffs. Spray carb cleaner didn't do much other than kill. The idle is steady and constant unless it stalls. I have an old style dwell/tach I can't figure out where to connect to get a tach reading. Timing: the timing light shows timing is at T-0 degrees. It advances as the idle speed increases. Playing with the timing base (pulser coils) makes it run faster and advances the timing. The timing adjustment has to be screwed all the way (the fastest idle) to keep the engine running otherwise it stalls quickly. Primer bulb is fine, doesn't appear to be a fuel issue; no problem reving up just poor idle. Tomorrow I will do some more tests. Any suggestions would be helpful. Sorry for the "book"; it gives the whole story.

jim dozier · May 18, 2004

Re: 1991 Suzuki DT 85 Intermittant Spark

If you haven't done so already you should probably rebuild those carbs. The Mikuni carbs like to be clean. They need to be disassembled and rebuilt. I would replace the crankcase seal if you think its leaking or not right. You say that unplugging the spark on #2 speeds up the engine

, makes me think your timing linkage is way off or your spark leads are on the wrong cylinder. After you rebuild the carbs make sure your carbs are properly synchronized with the ignition timing linkage.

1991 Suzuki DT 85 Intermittant Spark

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