'65 Pan-Help needed

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'65 Pan-Help needed


Post by Johnny » Wed Jun 15, 2005 2:06 pm

Gentlemen, I have been enjoying the forum for a few weeks....learned alot. Have expended my knowledge to fix this problem, so will appreciate any input. Purchased bike in January 2005. Front sparkplug fuel fouls, rear runs lean. Sounded simple to me, but the following is my list of eliminations.
1. Intake manifold is not leaking, tested with 15psi not only once, but twice.
2. Compression reads 115 psi front and rear.
3. Installed late 50's Chev. Points, (run them in my other bikes) and gapped correctly.
4. Running H.D. 3-4 sparkplugs.
5. Timed correctly and auto advance weights and springs appear good.
6. Have two M74B carbs, the one which came on the bike (boat anchor brass float) and an NOS with original cork float, runs the same with either carb. (Cotton is forwarding new floats) Jet is #19
7. New coil, runs same with either one. 5 ohm
8. New plug wires, had resistor wires when purchased.
9. Pulled exhaust, thought it might be plugged at the flattend area between case and frame, all is open.
10. Installed ignition booster (Thanks Kell) last night, spark went from dull orange to a snappy blue, still fouls front plug.
11. With a new set of plugs, bike starts good, idles good, runs down the road as follows: At any constant RPM the motor falls off (nose dives), under acceleration at any speed it runs great.
12. Running 6 clicks out from starving on the low speed needle and 1 1/2 turns out on the high speed (adjusted with motor hot).
13. Temps. (using a heat gun) are running close to the same front to rear on cylinders and heads.
14. No unusual engine noises.
The motor had a top end rebuild just prior to my purchasing it, by a proven local shop (personal friend). I have put approx. 750 miles on it basically trying to dial everything in. Only thing I can think of is possibly one or more valve guides (bronze) was set up too tight and upon expansion is creating just enough drag to alter valve movement with the cam??? Far fetched but i am grasping at straws here.
This is my first pan, as my other bikes are flatheads, knuckles and an F-Head. Any input appreciated, sorry to be so long winded but difficult to ask for help without giving you a starting point.

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Post by Cotten » Thu Jun 16, 2005 12:57 pm


When testing the manifold, are you using a constant supply of air at 15psi?

Did you test the pancover screws over the intake ports, particularly on the rear head?

Casting porosities are not unusual, both on manifolds and heads themselves, so I spray soap everywhere. Then turn the motor through until the intake valve opens, and test around the sparkplug, and even let soap run down the headgasket seam, especially under the exhaust ports.
(Dishsoap is corrosive, so I wash everything down afterwards!)

Have the heads had seat replacements? (Beware of inserts that have cracked into the port.)

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Post by Johnny » Thu Jun 16, 2005 2:11 pm

Thanks for the reply Cotton! Yes I used a tester with a regulator, continuous air supply, mating aluminum plate and gaskets to the intake manifold. Sprayed the complete top end. As previously stated even second guessed my effort and did it again. It points toward an intake leak, just haven't found it yet. My direction after putting the exhaust system back on last night is to run a hot compression test and determine any change from the cold test performed. Regarding the valve seats, they were in good condition and dressed. The heads were magnafluxed. The bike appears to be a relatively original un abused machine, but you can never tell what a previous owner has done until you find it. This is a hobby for me, a vent from the rest of the world. I will eventually find the problem......took me a while to determine the previous owner of my '48 Chief had installed the rods backwards. Just not something you would expect to be done wrong. Again, any direction greatly appreciated.

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Post by suicideshovel65 » Fri Jun 17, 2005 8:54 am

Just a beginner, but maybe I can learn something by putting some ideas out there.

My bike had the "manifold leak" in the *carb* not the manifold! Someone had drilled a hole into the carb body near where it mounted to the manifold. Not saying you should pressure test the carb - I have seen Cotten's reasoning for not doing this in a previous post - however it might be worth giving it a look over for non standard passages etc.
Of course this wouldn't explain the difference between plug readings at each head, but just thought I'd offer it up as a potential cause for the power loss.

What about a short or problem with regulator or charging system? When my bike's regulator was shot, every application of brake or indicator would cause the bike to die, however it would "run" and gain power etc under acceleration.



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Post by Johnny » Fri Jun 17, 2005 1:24 pm

Thanks for the reply and input! I can relate to the beginner statement, the more i learn about these old machines the more i find out i don't know squat. I think my carb. is performing correctly, will be better after i install Cotten's float....really like the concept of his float allowing fuel volume in the bowl to return to (or exceed) the original design. Additionally as previously stated i have run two carbs. with same results. I'm not an electrical expert but have run continuity test on all wiring related to the ignition, visually inspected were possible. Checked voltage at the coil with bike running. Generator is doing its job, battery stays up. Have even put a load test on it and all is well.
Leaving for the Early V-8 Nationals this weekend, pan will have to wait until i return. If there are any other "Flatheaders" going to Georgia, see ya there. Like my Pan but Flatheads Forever, bikes and cars!

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Post by fourthgear » Tue Jun 21, 2005 3:01 pm

Continuity does not always mean it will funtion at all levels . I would try a new plug wire in the front cyl. and a plug to match , just for shits and giggles . What kind of plug wires are you running ?

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Post by SkyHogg » Thu Jun 23, 2005 8:33 pm

Just to expand on what Suicide said (and this does not sound like Johnny's problem) I had a bike that would run OK at idle, but when power was applied it would only hit on one cylinder (and always the same cylinder). Turns out that a weak battery could not keep up with the power needed to operate at RPM above idle ... but it was just fine at low RPM.
Again, this does not sound like Johnny's problem, but just something to keep in the back of your mind in case you ever see it happen.
(Also, I was experiencing this with a vertical twin ... I like to mess with Brit stuff from time to time when no one is looking ... sorta like dating an ugly girl that's very willing, ya' know?)

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Post by wheels » Fri Jun 24, 2005 1:30 am

Johnny, had a similar problem last year with my 65. my problem was finally solved when my genrator shot craps and i replaced it. my bike would run good for a while then start to miss and foul the front plug(usually). iguess it would draw down the battery and then foul the plugs. just a thought. its easy enough to check your charging system. good luck.

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Post by Johnny » Mon Jun 27, 2005 3:56 pm

Thanks for the replies and suggestions. Been out of town enjoying my other passion, flathead fords. Going to get back on the pan this week and will keep the progress updated. Plug wires are solid copper, battery is new and charging system checks out good. Very close to throwing my hands up and putting it on the dyno (no full pulls here, just steady state tuning). Have utilized the dyno for fine tuning on my knuckles and flatheads, and look at it as a last choice for troubleshooting, but I think I'm out of guesses on this bike.

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Post by Cotten » Tue Jun 28, 2005 12:26 am

Please take this reply in earnest and in good faith, with no insulence implied:

Throwing quantities of money at a bike never fixed anything,.. except maybe a bad marriage or two.

Factory design works exceedingly well when all is in order. That's where the legend came from!
Adding modern gizmos only multiplies the variables, and hides festering injuries with a band-aid, and rots the core out of any resale value afterward.

But I'll defend to the death your right to booger it any way you want to. I enjoy it myself.

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Post by Johnny » Tue Jun 28, 2005 3:33 pm

Cotten, Thanks for the reply, and no offense taken. I agree, in principle, that we should respect the factory engineering and enjoy the bikes as built. But as stated, on bikes that are "riders", it is difficult to leave them alone and not play a little bit. Which sometimes bites us in the butt! On this bike, I'm basically trying every option I can grasp before digging deeper, inspecting cams, lifters, valve springs, etc.... Might seem strange to some, but I enjoy the troubleshooting aspect of the hobby. I'm blessed to be the "caretaker" of several bikes, and get bored if their all just running good.......lets make them run great. As stated in my original post, this is my first pan, and I am (with the input of folks like yourself and studying everything I can find) learning the design and characteristics of the engine. I'm slow, but I will get there.
Thanks again for the input!

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Post by Johnny » Tue Jul 05, 2005 8:09 pm

Well the good news is that the pan is running fantastic! Rode a couple of hundred miles this weekend and all is well. The bad news is I am not sure of exactly what fixed the problem. The only suspect was upon re-inspection of the plug wires I noticed the terminals on the coil end were not soldered to the wire, just folded back and terminals crimped. Looked a little suspect so I soldered and reinstalled. Got so frustrating towards the end that I changed multiple parts without test riding. Thanks again for the input from folks on this forum! Ain't life grand!


61 pan


Post by Jim » Sun Aug 07, 2005 3:26 am

After reading about your problem with the 65 pan, it mirrors my problem with plug fouling. The front cylinder fouls and the rear runs lean. The bike runs and idles good for awhile. Being stuck in traffic can be a problem! Usually end up running on one cylinder. A hotter plug seems to help--RJ18YC. What float do you recomend? The bike is original. I would prefer to run stock carb. Thanks

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Post by Jack_Hester » Sun Aug 07, 2005 11:09 am

Jim -

Get one of Cotten's killer float replacements for your Linkert. If the rest of the carb is in good order, this will bring new life to your machine. He hand-makes his floats out of a material (I can't even remember what he said it is) that is unaffected by the variety of fuels that can attack the OEM floats (not speaking of the brass ones).


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Post by Cotten » Sun Aug 07, 2005 12:32 pm


The difference in plug burn is most often an airleak that is best located with airpressure and soapsuds.

But why are you running resistor plugs?

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