Suzuki DT 140 '86, 2 cyls. dead

[lkcavanaugh]

1986, very low hour, freshwater only just lost two bottom cylinders; not firing at any rpm's. Compression is 145 while cranking. IC and ignition coils check to specs but TPS is not as pictured as in Clymar's; reading 0 ohms static, not tested running. Squirting gas into bottom 2 cyl no change. Fuel system good. Misfires at idle out exhaust, then it dies. Gear counter resistance 170 but output only 1.5VAC while cranking. pulser coils 155-165 ohms, but only .2vac while cranking. My (low) voltage test of pulser and counter coil is baffling me. Dealer inspection cost me $150 and he said ignition system these models virtually bulletproof, and mine is good. He said '86 and up had multi piece cranks and mine twisted between 2 and 3 thereby throwing off either timing or fuel in cylinders. Bottom 2 plugs are wet, somewhat carbony due to misfiring. There's no vibration or wobble on flywheel, motor never abused or "locked up" as with waterski rope wrapped around prop. Dealer says new crank required and total estimate is $2600. After hearing that I went home and checked tdc and bdc of pistons with measuring device through spark plug holes at 90 degree CW rotation and found all pistons measured the same at 90 degree intervals so I don’t think it’s twisted much, if any, (although I didn’t use a depth micrometer). Am I getting ripped? Value of this motor is not worth cost of repairs. Any suggestions

 

[jim dozier]

Re: Suzuki DT 140 '86, 2 cyls. dead

Do you or do you not have spark on all cylinders? Get an inexpensive spark checker at an autoparts store. You checked the compression on the bad cylinders and it looks good. Although I have read of twisted crank problems on this board I would not think that would be the first thing to focus on unless you had evidence such as out of sync piston measurements. If you have strong spark, properly timed, good compression, and fuel/air mix it has to fire.

 

[lkcavanaugh]

Re: Suzuki DT 140 '86, 2 cyls. dead

Thanks for reply. Yes, there's spark. No one sells spark testers anymore, I used plug with extended ground wire. Spark about same intensity all cyl. With Suzuki IC one can't adjust timing (or anything). So there's spark, fuel, compression, but what needs to be determined is: is there spark/fuel on bottom 2 cyl. at ... degrees before tdc simultaneously. (I don't know when it's supposed to fire. The puzzle continues/.

 

[jim dozier]

Re: Suzuki DT 140 '86, 2 cyls. dead

You might also check the fuel pump. If it has a hole in the diaphragm it will inject raw fuel into the cylinder to which its attached, causing that cylinder to run rich and not very well. But that wouldn't explain the other bad cylinder. Hope its not the crank.

 

[lkcavanaugh]

Re: Suzuki DT 140 '86, 2 cyls. dead

Fuel pump isn't leaking. I removed it, pumped up bulb, nothing came out of hole to crankcase. Guess I'll have to go for more professional help. Even Bill Kelly at Mastertech seems to be stumped with this one. I'm still stumped too, with real low voltage readings on pulser and counter coils and spark doesn't seem real strong either, yet dealer said ignition system all ok.

 

[otis_my_man]

Re: Suzuki DT 140 '86, 2 cyls. dead

LK, this is bringing back some baaaaad memories. I too have an '86 DT140. Back in '95 I fired it up on the trailer while launching like always and it started idling very rough and weak and would die after a few seconds. Attempting to rev the motor would kill it quicker. I spent several days checking spark, tank venting, primer bulb, fuel lines, carbs (disassemble and clean), reed valves, TPS, etc. to no avail. Drove me nuts. I finally admitted defeat and took it to a dealer, possibly even the same dealer you did (on the waterfront in Everett). Drove them nuts for several days too - they even replaced all 4 carbs on ths hunch that one or more may have cracked somehow. No help. Turns out that there was a metal seal on the crank between cylinders 2 & 3 that failed and was allowing the incoming fuel/air mix to be pumped between those cylinders through the crankcase without much reaching the combustion chambers. The fix was... yep... replace the crank. $2300 later, all was well and it continues to run great 10 years later. They said it was a freak occurrence and they had never seen anything like it. I haven't seen anything on this forum to disprove that, but your symptoms sound much too familiar. Hope you find a better / cheaper solution, but thought you might want to hear about this...

 

[mailman1]

Re: Suzuki DT 140 '86, 2 cyls. dead

I too have a 1987 DT 140. Bought it new in 89 and in 94 I had a mechanic look at it before the season and he heard it with one of those hearing things the doctors use, and said it was on its way out. I saw the crankshaft when it came out of the engine and the main bearings were bad. Replaced the crank and it is still running great.

 

[lkcavanaugh]

Re: Suzuki DT 140 '86, 2 cyls. dead

Thanks for recent posts. Been away from email for a while. I squirted raw gas into cylinders 3 and 4 while it was running to no avail, which troubleshooters said would probably rule out the seal problem and lack of fuel to the bottom cylinders. I'm taking it to another dealer tomorrow for another diagnosis. I will post diagnosis on this when received. I've got my fingers crossed.