1931 4 running VERY HOT

[1931 Four]

Last year I purchased a restored 1931 4. It currently has about 450 miles on the rebuild. It ran quite well last summer, but I could tell there was some fine tuning needed and a thing here or there that needed some attention. This summer however the adjustments I've made to the carb to get it running better went so lien and hot that it blistered the aluminum manifold. Let me tell you how I have the bike set up currently and see if someone can help from there.

First off, I'm in Salt Lake City at about 4,800 ft elevation, so my air is a bit thin. I have the intake valves set at .004. The exhaust valves at .008. I've refaced the exhaust header surface to get it milled flat and have installed new exhaust gaskets with gasket seal to try and close off any exhaust leaks. I have a new gasket between the carb and the intake manifold. As far as I can tell the engine is sealed up pretty well. At least as well as a 31 can be I guess.

I recently talked with Tom Cotton to learn more about my carb (schebler dlx). He indicated I should start the carb adjustments at 3 turns out on the low idle and 1-1/2 on the high idle. At that setting the bike starts easily and achieving a decent idle at full advance is not an issue,(I would however like to know about what the RPM's should be at idle at full advance).

At that setting however the bike is just under powered and backs up with fuel. If I lean out the low idle screw (screw on the exterior side of the carb) a 1/4 to 1/2 a turn the bike smooths out and starts to pull like I'd expect, but then it just starts running super hot. So much so it blisters the manifold, again! I shot the cylinder heads with a heat gun after a quick test 10 minute test run and I have head temps of 350 to 390 degrees, so hot it's turning my head gaskets into charcoal, literally turns them to black dust. What's frustrating is I didn't have this problem last summer.

I'm adjusting the low idle after the bike is warmed up with the bike fully advanced and at 3 turns out I'm getting a black sooty exhaust. From there however I'm at a loss of what to do next. It seems I'm going from to Rich to to Lean and hot withing a click or two of the low idle adjustment.

So......What am I missing? Do I have the low and high idle screws reversed and am making the wrong adjustments? Could it be something internal of the carb such as the float? I'm out of ideas and would really like to avoid frying the engine. If anyone out there can give me some input or better, yet a step by step guide on how to get this figured out, I'd sure appreciate it.

Thanks for your help!

[slamiste]

Somehow I imagine this will be a subject of much discussion and disagreement, but here's how I adjust the DLX on my 36 Indian Chief and all the Linkerts on my other bikes, including a 1939 Indian 4 (wrong carb).

I start with the low speed needle backed out from seat position 3.5 to 4 turns and the high speed needle backed out 1.5 turns. This should start the bike in a "rich" position. After the bike is completely unchecked, warmed up and at idle I turn the low speed needle in one notch at a time (slowly) until the bike misfires. At this point I turned the low speed needle back out 1/2 a turn. For high speed adjustment I take the bike on a ride to a location where I can quickly accelerate and back off a number of times. As long as the bike accelerates without hesitation I back off the throttle and turn the high speed needle in one notch. Accelerate again. If the bike accelerates without issue back off and turn the needle in another notch. Repeat until the bike hesitates on acceleration then back the high speed needle out 1/2 turn.

This procedure works well for me but even among my local buddies, everyone has their own technique.

Good Luck!

Steve Slaminko

[T. Cotten]

That's pretty universal, Steve!

(Except I squint and hold my tongue in my lip just right.)

But that's assuming all things are in order, and checking for vacuum leaks is a lot easier on twins.
Carbs are forgiving. Inlet appliances are not, and I can't imagine how you test any Four absolutely.

Suggestions, Four Folks?

....Cotten

[1931 Four]

Steve, any thoughts on the gap I'm running on the intake and exhaust? As mentioned I'm currently at .004 on the intake and .008 on the exhaust. I've been told to set the intake at .002 and most literature I've seen also calls for this setting, but at 4,800 foot elevation seems it might be better to run at .004 or so. Any thoughts?

[slamiste]

On the 39 I'm using the specifications call out in the Indian Four Overhaul Manual 2nd Edition. Cold Engine - Intake clearance .002, Exhaust .006. This manual only covers the 438 - 442 Models. Sorry but I have no experience with earlier fours or with higher elevations. While I'm far from understanding the EXACT science of valve timing, I don't think a couple thou extra clearance on the exhaust would make much difference. In any case If it was me I'd probably set the exhaust clearance to .006 and adjust the carb as I outlined.

Cotton's correct on the problem with vacuum leaks but I've got no suggestions on how to check for them on a four.

[1931 Four]

thanks, every bit of input helps a ton.

[Tom Wilcock]

On my 440, warmed up and at idle I turn the low speed in one click at a time until the engine starts to miss. I then turn the low speed out one click at a time (and count the number of clicks) until the engine starts to load up. I then turn the low speed back in 1/2 the number of clicks I turned it out. Set the high speed as previously outlined and then recheck the low speed.
Tom

[Tom Wilcock]

I know of an owner of a 1929 Indian four with sidecar who was given the bike as a birthday present by his wife. He had never owned a motorcycle before. Apparently the oil dipstick blade had fallen off the cap. He assumed it was like a car and the oil level would never go down so never checked the oil because there was no dipstick. The engine got so hot the aluminum exhaust manifold actually melted off. These engines require that the oil level be kept to the full mark Also a light enough oil to get lots of flow through the bearings instead the pump bypass. Cooling for the top end depends on lots of oil being flung from the rod bearings to the cylinder walls and piston undersides. The original early Indian 4 riders manual calls for #30 oil for temperatures up to 65 degrees.
Tom

[1931 Four]

thanks for your thoughts. It's about 95+ degrees around here right now so I'm running 50 weight. I would think that would keep me in the safe zone, but I'll double check and make sure the oil level is topped off.

[1931 Four]

One additional question or comment from your previous post, when your making your adjustments where is your advance set while making the adjustment? Are your making the adjustments fully retarded, half and half, or fully advanced?

Thus far I've been fully advanced when adjusting the low idle screw. Maybe that's not the position I should be using????

[slamiste]

Full advance is correct.

Steve Slaminko

[PRG]

Howdy sir,

First off a Four is rather a fragile machine compared to nearly any v twin and I would caution anyone in operating one overly hot through poor carb or ignition settings or both, especially when fitted with Babbitt bearings and those in the rod big ends. A motor attempting to seize will stress and pound out the rods resulting in reduced oil pressure.

Any idle settings should be achieved with ignition fully retarded, advance is there for just that, to chase ideal combustion which fully engages (max cylinder pressure/torque) at about 15-20 ATDC on most engines across the reve range. How much lead you require to achieve that efficiency is a learned skill, as a heavy rider in an extremely hot climate I have never ridden my Fours solely on full advance while underway over all operating conditions. One works the advance under load to where the motor feels free, not labored, and no more, running fully advanced at lower revs cokes your combustion chambers and fills your oil with abrasive carbon .....much faster than it would have done already. With the low speed needle adjusted correctly on a low rom level idle you should be able to roll of in 1st fully retarded feeding in advance with no motor hesitation. You’ve probably covered the carb problems with Cotten, make sure your ignition is timed correctly. Unlike later Fours you have the luxury of a timing plug in the top of your flywheel compartment case.

It’s been a long time since I pulled the top end on a pre-38 but these later cylinder head pairs are not indexed/doweled in the cylinders so to alleviate some possibility of intake leaks one must lightly clamp up the intake manifold to the heads loose before torquing the latter. If I recall your era motor is not doweled so provides the opportunity to do the same. You might want to lightly spray WD40 around each intake port gasket at idle to see if the revs go up or down which would indicate a leak before undoing anything.

[bernhardt]

The early fours had what I call a 'bridge' intake. The cylinders are cast individually, and the manifold is a single casting that bridges all four cylinders. The 4 cylinders are each bolted to the case and if they move the connection to the manifold may open an bit making an air leak. After the motor is warm spray some wd40 at the connection between the cylinder and the manifold, and listen for a change in idle. If it is leaking there, the manifold has to come off, new seals, and possibly cylinders shimmed. Be careful tightening the cylinder base nuts, the ears will break if they are over tightened.

[T. Cotten]

What would happen, Folks,...

If you yank the carb on a Four, and pressurize the manifold to a regulated 15psi, even though all the valves aren't shut?

I never had the pleasure. Thanks in advance,

...Cotten

[PRG]

Howdy chaps,

For anyone reading this thread having a 38 later Four and at the point where they have the cylinders secrured to the top case and are ready to do the top end be aware the cast alloy intake manifold on these motors is very fragile. If running heat riser tubes assembling the top end can be fiddly while at the same time trying to get the best manifold seal to the heads as it cannot in any way be torqued to down to achieve a seal that is not there to begin with. Any desired gasket crushing, though not encouraged, should be limited to the robust exhaust side and if much required in new not old annealed exhaust studs.

Loosely fit the heads onto the cylinders with only those head bolts accessible with the intake manifold fitted. Lightly tighten the intake manifold down, and torque exposed head bolts to 20 ft lbs or so. Remove intake manifold, fit remaining head bolts and if running copper gaskets on known flat surfaces torque all to 30 ft lbs (manual recommended torques are for prior inferior fiber based gaskets and destructive to these now 80 year old alloy castings causing crush at the washer lands). Refit intake manifold without fastenings at the same time as risers and exhaust manifold. Do not be tempted to hone riser inserts in either manifold to achieve an easier fit. Heat at the exhaust ports along with a heavy poor heat dissipating iron exhaust header will require utmost caution when fitting nuts to original studs. These machines experience very little exhaust back pressure in such large ports and mufflers with no baffling therefore nuts need only be lightly cinched on machines with known flat aligned mating surfaces.