I need advice I flooded my M38A1 While starting it this morning,After getting it running I headed off to Ma's & Pa's for a visit 150 mile round trip, it backfired often around 45mph out the exhaust, above 50mph under load it did not backfire. I have a carb rebuild kit but it is marked M38 on the box, did they use the same carb? I know that the carb was not done when the engine was last overhauled 20000 miles ago. I have suspected the carb all winter but it started to good to mess with. it burned a tank of gold today so maybe I should lay it up and do the carb. ANY ADVICE WELCOME.
No, an M38 & M38A1 do not share the same carb, & the rebuild parts kits do not interchange. While I am definitely not an expert on the carbs, it sounds like a diaphragm on the A1 carb could be going bad, as they are want to do. Wes K can probably answer this one with his eyes close.
The old NOS kits and foreign manufacture kits are not good for todays rebuilds using todays fuels.
The only quality kit out there are the Carb Shop's and The kit that john at Midwest Mil and AJP sell. These contain modern rubeer materials that are compatible with the modern fuels. The kit that Midwest and AJP sell are $55.00 and apply to both carbs. This means they put all the parts fro both carbs in one kit. It does mean the carbs are a lot alike. They are very similar but the porting and barrel sizes are very different.
A carb that suddenly floods or suddenly runs too lean generally can be repaired by overhauliong it but I'd try a little troubleshooting first.
1-Check the two diaphrams by removing the two diaphram covers. If one or both have failed replace them. This can be done without removing the carb. So can an inspection of the float and it's valve be done without removing the carb. These sudden malfunctions can gemerally be corrected without a complete overhaul. If the problem dictates complete removal and disassembly then by all means get a quality kit and overhaul.
Thanks for the info I'll check the diaphrams tomorrow. I cleaned the kit box, it is marked M38AL NAPCO I got it from Niagara Military Parts. I have the phone # if any one wants.
whitch liquid gold is best for an f head regular or high test. Should a person run a gas additive? Afriend of mine did the engine 15 years ago when he owned it so it should have compatible valves & seats. A recient compression test showed no issues
You don't need anymore than 80/87 octane mogas. A little leaded fuel mixed in or some lead substitute would be a nice tough. You can buy leaded fuel at your local airport. Pick up 2 or 3 five gallon cans of 100 Low Lead (which has a lot of lead in it) and mix it in at say 2.5 gals 100LL with each full tank. The two improvements needed to deal with the hotter running unleaded gas today is the hardened valve seats and steelite exhaust valves. Also make sure all your rubber diaphrams in the carb and fuel pump are modern materials. With the 100LL added you can bump the timing up to about 8 BTDC.
I'll have to mix a brew and try it out,might be just the edge needed. Thanks as the WAR dept. and I tip the scales close to 500lbs. and we want to run some trails this summer with the local jeep club.
Still can't find an exploded view of the carb. I think that the throttle shaft may be a little loose in the housing. ARE there bushings in the housing? This may require a trip to Dads to use his machine tools.
Thats great Wes. Really ups my comfort level to have a diagram. I got the M37 cranked up today almost ready for Provincal saftey inspection. Should soon bolt the top on and put the M37 out and the jeep in for a carb overhaul and lube inspection.
I flooded my M38A1 While starting it this morning,After getting it running I headed off to Ma's & Pa's for a visit 150 mile round trip, it backfired often around 45mph out the exhaust, above 50mph under load it did not backfire. I have a carb rebuild kit but it is marked M38 on the box, did they use the same carb? I know that the carb was not done when the engine was last overhauled 20000 miles ago. I have suspected the carb all winter but it started to good to mess with. it burned a tank of gold today so maybe I should lay it up and do the carb. ANY ADVICE WELCOME. 
Thanks for the info I'll check the diaphrams tomorrow. 
whitch liquid gold is best for an f head regular or high test. Should a person run a gas additive? Afriend of mine did the engine 15 years ago when he owned it so it should have compatible valves & seats. A recient compression test showed no issues 
Still can't find an exploded view of the carb. I think that the throttle shaft may be a little loose in the housing. ARE there bushings in the housing? 
This may require a trip to Dads to use his machine tools.
and the jeep in for a carb overhaul and lube inspection.