I need a little help last fall I purchased a 1969 930CK (941) it runs on propane. This week is the first time I have really used it hard before this it was just running a brush hog. This week I was going to use it to run a round baler but before I could make one pass around the field I noticed it was struggling under the load, and it backfired and blew the breather apart. At that point I switched to our 4020. After putting that back it ran fine not under a load. I have begun trying to check the timing and the settings on the carb. Question one one the timing I found two setts of marks on the crank pulls. One had three marks close together the other had several hash marks and 35 on one end of the marks and 20 one the other. Which one of these set of marks is correct one to use right now ti is set half way between the long set of marks with the numbers on it. The other problem is the carb described in my manual is not at all what is on my tractor. Mine has an Impco model 100. Can anybody tell me is this the correct carb for this tractor. It only has one adjustment it says for idle. But I took that screw completely out wile,the tractor was running and it made very little difference in the sound of the engine. If some this is not the correct carb can some one please tell me which one is. If this is the correct one can someone please tell me how to set it correctly. Any pics of your 930Lp system would be great.