Starting problem, Engine rotates almost to TDC and stops

Questions regarding the DR800

Starting problem, Engine rotates almost to TDC and stops

Postby dr800s97 » Mon Dec 18, 2017 8:14 am

Hi all, i have a DR800s 1997, Engine has the auto decompression system.
I have an issue with rotating the engine by the starter, I press on the starter button Decompression system engages engine rotates almost to TDC and stops.
At that moment the starter struggles his wires get hot and the engine wont start.
I removed the magneto cover and even with the cover off the problem is present.
If i remove the spark plug engine rotates freely and no problem encountered.
Disassembled the starter cleaned it, brushes are in great shape reassembled it and still same problem.
Wires are good Ground is good not problem with that and i use my car's battery while the engine was running so no problem with battery.
Looking for help from the pro's here because my DR is not moving anywhere :(
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Re: Starting problem, Engine rotates almost to TDC and stops

Postby BigBob » Mon Dec 18, 2017 10:13 am

If it turns over with no spark plug ie with no compression, but will not turn over with compression, I would suggest that your decompressor relay is not working properly.
You can reach under the tank and push the decompressor shaft lever back with your thumb and then try again with the starter.
If this works, then you should convert the system to a manual one as on the SR41/42 and not have any more trouble.
I can`t think of anything else that could cause your problem unless lots of fuel has leaked into the engine through the carbs
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Re: Starting problem, Engine rotates almost to TDC and stops

Postby dr800s97 » Mon Dec 18, 2017 11:12 am

Hi, thanks for the reply.
Decompress-or solenoid works, when i press the starter switch it engages and then after 1 turn it disengages but the engine wont start.
After 1 turn the engine stops from turning, the Starter is fighting with the compression and eventually passes it until next cycle.
If i manually push it and lock it in ON position the engine spins freely but wont start.
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Re: Starting problem, Engine rotates almost to TDC and stops

Postby O.R. » Mon Dec 18, 2017 5:47 pm

A selonoid that works does not mean it works OK. You have to check the actually functioning of the decompression shaft. There is a chance that the cable has to much play. The selonoid just works 0,2 second. Do you really hear the decom shaft returning (click!) after you pushed the starter button? Anyway, try BigBob's tip to open the decompression valve by hand or with a piece of rope. Than you can also open the decomp valve longer than those 0,2s.

Another point of view. My rebuilt engine started easy @ first. After a while, the starter motor didn't have te power (speed) to make the engine start. Even with a second car battery. Turned out te be that since my engine was running in, the compression reached the end level and that obviously was to much for the starter motor. It does not seem to be unusual for starter cables to wear because of age. Problem was solved by using new and heavier starter cables.
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