Suzuki DR 100 no start - Motorcycle-Journal Forums

VW cat · 05-06-2006, 07:08 AM

Baffled by this one. Just got this early '80's bike, owner had spent alot on it and engine work included new valves, piston rings and timing chain. He said he had it running but could not get it started, when we wanted to buy it.
Engine will only fire only occasionally. Spark appears blue and very strong across the new correct NKG plug. Carb was clean inside and full of fuel, so we blew out the jets and made sure the orfice in the bowl was open( starting circuit). Mixture screw re-installed at 1 turn. Placing a hand over the carb while cranking draws fuel. Plug gets wet if the choke is left on. Fuel supply to carb is good.
Compression with one of those old rubber tip testers is 90, then 120 lbs. as cranked. Cam timing appears correct with the valves alternating at TDC. and the exhaust valve closing a few degrees after the start of the compression stroke. No air leakage back out the carb when cranked. Exhaust pipe is clear, exhaust valve has clearance.
I pulled the cover off the engine, not realizing that compartment is lubed, and using my old battery powered timing light from the '70's, got a check of the timing. Locating the marks on the flywheel and housing, and verifying with the piston movement; it fires about 3/4"from the housing TDC mark, in advance(clockwise). Seems to be the 13 degrees initial my manual states or is something wrong here?
Starting fluid ( hated to try it), gets the same result, a rare puff out the exhaust.
The only thing I noted about this engine was the ease with which it cranked over, guess it's not like an old BSA. Also we had to add motor oil to the engine, it was very low. My next step was to have the coil tested. I have not squirted oil in on the rings yet to see if they are washed.
Would someone give me advice on this, I clearly have not been troubleshooting this logically.

**Clint** · 05-06-2006, 11:14 AM

Wow. That is by far the most thorough and informative diagnostic post I've ever read. Bravo!

Welcome, cat. My only thought: Is the cam 180 degrees out? I don't know enough about timing marks to determine whether you've eliminated that possibility.

robertc729 · 05-06-2006, 07:30 PM

Wow, great first post, alot of information, Welcome to the forum and good luck getting your problem solved.

VW cat · 05-07-2006, 06:50 AM

Thanks for the replies. On 4 cycle engines, I have seen valves overlap( one closing as the other opens), always at TDC on the ''dead'' stroke. I was using my finger to check valve movement at this point, while feeling piston at TDC. It appears to be correct. Not sure how to find the cam mark.
I think the ignition must fire at TDC on every revolution of the crankshaft as I see no way of sensing off the cam...but if it did, would this explain everything? Firing on the dead stroke?

05-06-2006, 07:08 AM	#1 (permalink)
VW cat Newbie Joined: Apr 2006 Posts: 2	Suzuki DR 100 no start Baffled by this one. Just got this early '80's bike, owner had spent alot on it and engine work included new valves, piston rings and timing chain. He said he had it running but could not get it started, when we wanted to buy it. Engine will only fire only occasionally. Spark appears blue and very strong across the new correct NKG plug. Carb was clean inside and full of fuel, so we blew out the jets and made sure the orfice in the bowl was open( starting circuit). Mixture screw re-installed at 1 turn. Placing a hand over the carb while cranking draws fuel. Plug gets wet if the choke is left on. Fuel supply to carb is good. Compression with one of those old rubber tip testers is 90, then 120 lbs. as cranked. Cam timing appears correct with the valves alternating at TDC. and the exhaust valve closing a few degrees after the start of the compression stroke. No air leakage back out the carb when cranked. Exhaust pipe is clear, exhaust valve has clearance. I pulled the cover off the engine, not realizing that compartment is lubed, and using my old battery powered timing light from the '70's, got a check of the timing. Locating the marks on the flywheel and housing, and verifying with the piston movement; it fires about 3/4"from the housing TDC mark, in advance(clockwise). Seems to be the 13 degrees initial my manual states or is something wrong here? Starting fluid ( hated to try it), gets the same result, a rare puff out the exhaust. The only thing I noted about this engine was the ease with which it cranked over, guess it's not like an old BSA. Also we had to add motor oil to the engine, it was very low. My next step was to have the coil tested. I have not squirted oil in on the rings yet to see if they are washed. Would someone give me advice on this, I clearly have not been troubleshooting this logically.

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05-06-2006, 07:30 PM	#3 (permalink)
robertc729 Forensic Bug Splatter Analyst Joined: Mar 2006 Bike: 05 Boulevard C50 LE, 06 S40 (wife's bike) Location: Lexington, KY Posts: 4,086	Wow, great first post, alot of information, Welcome to the forum and good luck getting your problem solved.

05-07-2006, 06:50 AM	#4 (permalink)
VW cat Newbie Joined: Apr 2006 Posts: 2	Thanks for the replies. On 4 cycle engines, I have seen valves overlap( one closing as the other opens), always at TDC on the ''dead'' stroke. I was using my finger to check valve movement at this point, while feeling piston at TDC. It appears to be correct. Not sure how to find the cam mark. I think the ignition must fire at TDC on every revolution of the crankshaft as I see no way of sensing off the cam...but if it did, would this explain everything? Firing on the dead stroke?

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