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I have a 07 ata250c and I'm trying to find out how to set the timing. It doesn't have a timing chain like every other bike I've had. I see a dot on the cam gear but no corresponding mark on the gear opposite. A repair manual would be awesome but if someone knows would be greatly appreciated
The engine will probably be a copy of a Honda. However most Honda 250s were OHC and/or twins, so it could be a very stretched CG 125 engine. Take a look at some CG engines on-line and compare. There will be videos of how to time them. The prefix to the engine number stamped on the crankcase, is a help with identifying the "family" it is based on. My guess would be that cam gear mark will line up with a mark cast into the engine case, when on TDC.
When I was trying to find parts I couldn't find any for the ata250-c, however I found the ata250-d (utility version) that said it also worked for the gc200 however the crank and piston ended up being different.
attached is a pic of the stamp on the engine case.
First off, is it a pushrod single? If so I'm fairly sure it is a stretched Honda CG125. The 171FMM stuff on Google seems to indicate it is. If so it should have timing marks on cam gear and crank gear. Never done one myself but from CG125 videos, crank gear mark is not that important as the flywheel key should be upwards (TDC) when the gear is in the right place, so mark on cam should point to centre of keyway.
Ok, I had to have a new crank gear pressed on and the machinist didn't line the dot on the crank gear with the keyway but when I set the timing I lined the dot on the cam gear facing downward to the tooth in line with the keyway on the crank. I'm glad to hear you say the dot on the crank gear doesn't matter as long as the keyway is lined up. I just hope the cam lobe was supposed to be facing down and I don't have it 180 deg out.
I greatly appreciate you for the help, I've never came across this style of timing before.
Because ATVs have a "dead spark" (sparks every rev) you can't get it 180 out, turn the crank through 360 and the cam is then rocking the valves between exhaust and inlet stroke, with the timing mark pointing upwards. You can set the valve clearances 180 out, these must be set at the end of the compression stroke (TDC), when mark on cam is downwards.
Aug 9, 2021 | 07:09 PM
ATA250C timing help
