How (and where) do I check/set the timing on a 2001 arctic cat 250? It only runs on full choke. I've swapped out the plug, coil and s.plug lead. iIve had the carb apart and cleaned it. But still only runs on fulls choke, backfires and has no power. It runs better after a 10 minute warmup, but still requires near full chike to keep goig and have any power. Other ideas??

Thanks for any more ideas,

 

Geoids; First off what does you plug look like? The timing is suppose to be 5 degrees BTDC below 1800rpms and max out at 38 degrees BTDC above 3800rpms, however the is no adjustment. There is a plug on the left side of the crankcase cover that gives you access to the marks.

 

The plug looks wet - too rich. I've pulled it after a 10 min warmup to check it. If i start taking off the choke - the engine dies - even while moving. I thought maybe it was a timing problem beacuse other stuff seemed to check out.

 

If the plug is wet it would be too rich and choking would only make it worse not better. However the wetness could be caused by the choke. Have you changed the plug? I've seen them cause some real strange stuff. The timing on these things is all controlled by the ignition module. No mechanical at all. But it doesn't sound like ignition to me, but then again I've been wrong before. My next guess would be float level, low level means lean condition and won't run. This stuff is tough troubleshooting like this, really need the bike to real tell whats going on.

 

If you have to run with the choke on, then your pilot jet is clogged. The pilot jet is really small on the 250's. You may need a torch tip cleaner to remove the obstruction, or replace the jet. The backfiring/power loss is from running the motor with the choke on (lack of air).

 

Anytime you run a torch tip cleaner through a jet you open it up to a larger size, If you can just use air pressue to blow it clear or a strand of small steel wire(a bristle from a stainless steel wire brush), I would recommend you replace the jet.

 

If the pilot was opened up too much by cleaning - could that cause this problem? (i did do that torch tip cleaner attempt) What size jet for the replacement? The timing is really controlled by some electronics module (CDI?) and not changable? i tried spraying some carb cleaner around the carb-cyl boot while running to check for leaks - didn't notice any change in rpm. s. plug is new - I double checked it in another 4x4. I swapped out coil/plug lead, with no difference also.

 

According to my parts list the pilot jet is PN#4505-059 and is a #45. I found it here and I like this site as it lets me know part number and price before I buy.
http://www.alpha-sports.com/arctic_cat_atv_parts.htm
When this problem of needing the choke to run the engine came on did the bike sit awhile? You know like several weeks. Fuel goes bad real fast now a days and is very dirty compared to 15-20 years ago. I always run a filter on some sort any more.