72 JD 400 WILL NOT IDLE

Danzig · Post by **Danzig** » Wed Jan 16, 2008 4:06 am

http://z12.invisionfree.com/jdsleds/index.php?showtopic=2452

Maybe this old post will help.

Danzig · Post by **Danzig** » Wed Jan 16, 2008 4:15 am

The actual outcome of my X8's problem was the carb. the WRA-34 was changed to the 21. The original carb is in a box in pieces and still is today. JDFANPA even sent me a tested carb which I never needed. I lost much sleep over the same problems as you are encountering and to this day, I dont know what is wrong with the original carb. After upgrading to another carb, the sled is mean. I ran it at the HOF last year and had no problems with the WRA-21 carb.

400brian · Post by **400brian** » Wed Jan 16, 2008 5:07 am

As far as I know, in this case Joe has fewer options.

The '72s used a smaller flange carb that the later models.

So, while he might try a different carb, it will have to be the same model.

HoosierDeereMan · Post by **HoosierDeereMan** » Wed Jan 16, 2008 10:00 am

Brian,

What are the chances of replacing the intake from a later model 340 with the larger mounting flange. I don't know for sure but I think it would bolt right up.

flacker36 · Post by **flacker36** » Thu Jan 17, 2008 12:57 am

Evening all,

I picked up new plugs & checked the spark in the dark shop - both plugs looked real good with a good strong blue spark.

I took the carb to a local guy today & he put in a new diaphram & trimed the gasket that lays over the fuel pump spring.

I put the carb on & started it. I was able to get it to idle more than before & eventually with the high speed needle open to 7/8. The engine seemed to be viberating quite a bit & not running real smooth. It also seemed go up and down in rpms. Eventually it would die out if left to idle.

I did lift the back of the sled & it did NOT bog & want to die out - so that has changed.

The #2 plug is still a lot hoter to the touch than the #1 is. # 1 seems to be a little wetter also.

I pressure tested this engine 3 different ways I am sure I am not sucking air. But just to be sure I will test with starting fluid on Thur.

Sounds like I should go back & check the point gap & timming also.

The fact it will idle sometimes makes me think that the muffler is not blocked. It will bog & die with the muffler on or off.

Joe

HoosierDeereMan · Post by **HoosierDeereMan** » Thu Jan 17, 2008 4:17 pm

Can you explain more about trimming the gasket that lays over the fuel pump spring?

flacker36 · Post by **flacker36** » Thu Jan 17, 2008 6:13 pm

The gasket that lays over the fuel pump spring (the big silver dish looking thing) he trimmed back closer to the two tabs that hold it in the housing. He stated the gasket interfears with the full motion of the spring. He did not trim it all the way to the tabs, he took of an 1/8 of an inch just to free it up some.

I was able to get it to idle more, but it still ends up bogging out & then dieing out.

I am at witts end with this thing, Everything I try seems to change something else. I am going to test with starting fluid tonight just to varify no vacume leak.

Joe

HoosierDeereMan · Post by **HoosierDeereMan** » Thu Jan 17, 2008 7:46 pm

O.K. I know what you are talking about now. Yes, I have seen the gasket extend over those tabs. I've never really given that much tought. I'll have to make a note of that for the next time I rebuild a Walbro.

Are you using clear or a see through gas line from the tank to the carb? The supply line should be a solid flow. No air bubbles or anything.

When you set the timing on #1 and if you adjust the point gap on #1 make sure to recheck the timing. If you adjust the point gap it will change the timing. You may have to repeat this 2 or 3 times to get it dead on. You will need to do the same with #2.

Also keep in mind that when adjusting the carb if the exhaust burns your eyes it is too lean.

flacker36 · Post by **flacker36** » Fri Jan 18, 2008 12:10 am

I don't know that having the gasket trimmed really helped, but then again I think I have some other issues going on.

I am using clear fuel line for both sides.

I decided to take the engine out again and go over everything from top to bottom.

A couple of months ago I took apart the flywheel to inspect the cam, springs & governor weights - all checked out good. When I put it back together, I remember being confused on the verbage in section 40 (Electrical systems) page 10-20 that states: IMPORTANT: INSTALL CAM WITH CAM LOBE POSITIONED SLIGHTLY TO THE LEFT OF KEYWAY. (I have Kokusan Ignition)

Do you positon the cam to the left of the keyway while looking at it from the inside or from the outside of the flywheel. As I look at it today, I positioned it to the left from the outside. So if I'm looking down at the inside of the flywheel, my cam is to the right of the keyway. If I have this positioned wrong, could this be part of my bogging, lack of idle & eventually dieing out issue???????

Those of you that have SM2100 if you could take a look & tell me how you read it.

Joe

400brian · Post by **400brian** » Fri Jan 18, 2008 9:28 pm

The same description is in both SM2100, and SM2095 ( '71 ).

I would assume they are talking about left - right as you are looking at the backside of the flywheel while assembling the advance mechanism.

Honestly, I've never messed with these. If you don't feel good about it, I could pull a flywheel off and take a photo.

flacker36 · Post by **flacker36** » Fri Jan 18, 2008 11:53 pm

I agree, it should be positioned to the left of the keyway as you are looking at the backside of the flywheel. I also asked some other folks & they also agree. When I put it back together, I positioned it the wrong way. I do think this could effect the timing of the spark & thus effect fuel burn creating the a fuel rich/flooding situation.

I will do my complete engine check, positon the cam the right way & put back together.

I am soaking the muffler in parts cleaner & will hose out, air out & brush out Sat.

Thanks folks for all your help -- I will hope for the best with my engine check & reassembling.

I will keep you posted!

One last thing, Is there a gathering coming up where all the vintage sleds are heading to?? I heard there is something in Wis coming up.

Joe

400brian · Post by **400brian** » Sat Jan 19, 2008 2:32 am

This advance issue could be the problem.

I remember on our '72s back in the day, if the idle slowed down, you could hear an audible click ( the advance snapping shut? ) then the engine would spool down rapidly and die.

I've never heard this on the '74 sleds we are running now.

Anyway, I hope that takes care of the problem.

400brian · Post by **400brian** » Sat Jan 19, 2008 2:57 am

One last thing, Is there a gathering coming up where all the vintage sleds are heading to?? I heard there is something in Wis coming up.

Joe, look at the top of the General Talk page. RIDE with the Champs.
We are planning to get together on Feb 7-8 in Horicon, then on Feb 9 in St. Germain, WI

flacker36 · Post by **flacker36** » Mon Jan 21, 2008 9:06 pm

Brian - thanks for the info on gathering up in Wis.

I will be putting the engine back together on Tue - hope the cam issue ends up being my problem.

Will update then!

Joe

flacker36 · Post by **flacker36** » Thu Jan 24, 2008 12:40 am

Update!!

Well - it ends up that if you position the cam to the left of the keyway while looking at it from the inside of the flywheel, you will not be able to time the engine. You can set the points at .014, but when you go to time it - it is imposible. So I put it back the way I had it & bench gapped & timed the engine.

While I have the engine out, do any of you think the generating coils (Under the flywheel) could be bad????? (they are the only things I have NOT replaced).

If it idles with the High speed needle closed (and runs great at other rpm's) I would think it is a carb issue, not an ignition issue.

QUESTION:: I have been through the carb a billion times. I also took it to a local guy who knows a lot about these carbs & he said it looked fine. Would trying a different carb that has been rebuilt really make a difference?????

Joe