The Stovebolt Site Forums The Shop Area Engine Shop Rochester rebuild.....2nd attempt

Removed and tore down the Rochester B from my 216 again today. Discovered that I had installed the wrong gasket between the two halves of the bowl so put in the correct one. I also reexamined the check balls to make sure I hadn't put the wrong size ball in the wrong holes. All seem to be correct. Also read in the instructions that if you had a carb insulator that you did not have to use an additional gasket there, so I removed the one I had on top of the insulator. Bolted the carb back on, filled it with a splash of gas and started it up. After it came up to temp I took it for a spin. It still backfires, coughs and sputters when I take off, and when I shift through the gears. It runs much better if I pull the choke half way out. Seems when I mash the accelerator down it hesitates and seems starved for fuel. I pulled it back in the garage and raised the hood. I sprayed some carb cleaner at the base of the carb on the insulator connection and the engine started to die. When I stopped the spray it regained RPM's. This tells me there's a leak there. Would this be the source of my problem now?

Any ideas about what's making it run so rough?

Thanks a lot.

Check the carb base with a straightedge and a feeler gauge. You'll probably find that it's warped and allowing an air leak, or possibly there's a worn throttle shaft that's allowing air to leak. For the warped casting, draw-file it until it's flat. The throttle shaft can be replaced, or bushings can be fitted to the housing by reaming the holes oversize, then line-reaming the bushings after they're installed.
Jerry

It is also possible you could have more than just a carb problem. Check the timing and also make sure that the vacuum advance is working properly.
Fred

I think both posts are great advise. Sounds like your issues are more than the carb.

Sounds like you need gaskets on both sides of the insulator. Make sure the hole on the bottom of the carb has a passage in the gasket to reach the vacuum in the manifold. Make sure you have the float level set right & the power valve piston goes up & down & kicks the ball off its seat.
Throttle shaft wear on the B carb is seldom a problem. The base is cast iron & both sides have a long bore.

I'm no master mechanic, but I'm tryin' to learn! I'll take off the carb and inspect the base for warpage. I'm also going to put the gasket back on top of the insulator to help with that vacuum leak there. I'll read the shop manual and try to time the engine too. Haven't done that since I've owned it 4 years now.

Thanks for the advice!

Before tearing it apart, spray unlit propane around the base of the carb and the intake to head area. If you have a vacuum leak, the engine will speed up when it gets a sniff of propane. The vacuum advance can leak and cause a lean condition plus a running condition. Check the hose going to the wipers as well, or any other vacuum line you may have.

Sure sounds like a vacuum leak to me.

Joe

file the carb base bolt holes on the B you got sitting on the shelf.

Sounds exactly like the problem I am having with my '41, 228. Let me know if you figure it out! I'm checking timing and the hose to the windshield wiper tonight.

My '41 turned out to be that I had somehow reversed two plug wires...might be worth a check. Jim

Elmer46, you're funny! If that B fit I would have already put it on the 216 and given you mine!!

I'm hard pressed to believe that it's the timing since it ran fairly well before I tore it down to rebuild the carb. Something is just not right. I think the carb base needs that extra gasket sitting on top of the insulator so I'll reinstall that and give it a try. Short of that fixing it the only other thing I can think of that would have changed would be the needle valve. Maybe that's not set right. Backed out 1.5 turns is what the instructions said. Would a misadjustment on that needle valve be causing me any problems?

Thanks.

Sounds like we got our next meeting project. I've got a carter you can use.

The needle valve adds more fuel as you turn it out. It only effects idle, once the throttle is open just a little the main circuit of the carb takes over. Try giving it a few more turns out, go till you can tell the engine is running rough or you smell fuel in the exhaust. Once you find that point, go in till it starts to die or stumble, then back it out till it smooths out but not so far it over fuels. 2 to 2 1/2 is about right for most carbs, the fuel quality can effect it (ethanol).

Joe

Thanks for the comment about the needle valve Joe H. I'll try adjusting it this weekend.