Pre-detonation...ugghhh

Forum rules
Please do not start new topics here, but here: New Panhead and Flathead topics
Post Reply
65 Eric
Posts: 59
Joined: Fri Jul 13, 2007 10:35 am

Pre-detonation...ugghhh

#1

Post by 65 Eric » Wed Apr 04, 2007 3:16 pm

Description: The damn thing pings!

Gentlemen, I sure wish I had found this forum or at least someone who owned a Pan before I did the top end on my recently acquired 65 Pan. Thinking more is "gooder" I installed .030 over WIseco 9:5 to 1 pistons. I'm running an "A" grind (andrews) that was in there and I installed STD panheads (had shovels on it) with shovel intake and a CV40 carb. The damn thing pings! (no shit you say!) I've made sure the push-rods (solids) are adjusted, my timing is slightly retarded, I replaced the springs on the circuit breaker weights, couldn't find "heavy duty" ones so I just put new ones in, I put the insulator spacer between the carb and manifold, I'm running a two into one exhaust with a muffler, I changed the slow jet from a 48 to a 50, I've checked for intake leaks twice with the tester I made, (Thanks Cotten!) I changed to a colder plug and I even tried the J&P "Rocket Fuel" octane booster. Changing the slow jet made the biggest difference I think. I can still make it "ping" if I whack the throttle while at a low rpm or if I take off a little too quick. It doesn't ping until it warms up and the motor has only 500 miles on it. Is replacing the pistons with a lower compression ratio the only way to eliminate the pre-detonation problem I'm having? did I forget anything? any and all help is appreciated gentlemen as I'm now stuck for a solution. The good news is it starts easy and runs great but I noticed my plugs are white on one side of the electrode and brown on the other, almost perfectly split down the middle. Does indexing the plugs help?

65 Eric



Skip
Posts: 231
Joined: Mon Apr 26, 2004 11:18 pm
Bikes: 48 pan
81 shovel
01 softail std
04 heritage
08 roadking
72 ct70
Location: WV

Re: Pre-detonation...ugghhh

#2

Post by Skip » Wed Apr 04, 2007 3:24 pm

I think pre-detonation is from the points being set too close...or timing off...or combo of both...not an expert, just been THERE recently....Skip
by the way I used 7.5 to 1 cast pistons...best move I made this whole process...Skip

65 Eric
Posts: 59
Joined: Fri Jul 13, 2007 10:35 am

Re: Pre-detonation...ugghhh

#3

Post by 65 Eric » Wed Apr 04, 2007 4:04 pm

Thx Skip, I'll check my point gap and put the timing back to spec. and see what happens. Like I said I can make it not ping if I ride real conservative but that's no fun! and we haven't got into our 100deg. days yet. I got a feeling I should just go ahead and change the pistons and be done with it. Where did you get yours? and did you have to re-balance your flywheels like I read in a post by Mr. Hester? He was was referring to KB & S&S pistons only I think.

we'll keep ya posted,
Eric

Skip
Posts: 231
Joined: Mon Apr 26, 2004 11:18 pm
Bikes: 48 pan
81 shovel
01 softail std
04 heritage
08 roadking
72 ct70
Location: WV

Re: Pre-detonation...ugghhh

#4

Post by Skip » Wed Apr 04, 2007 4:29 pm

I got mine from a HD dealership....they are stock .10 over pistons....used Hastings cast rings too...total for the set was under $100.00...and no I did not need to do anything to the flywheels...I think...and this is from when I asked the question...if you use stock type pistons you will not need to balance as the weight will not be off by that much...Good luck...believe me I know frustration when it comes to these damn things......Skip

65 Eric
Posts: 59
Joined: Fri Jul 13, 2007 10:35 am

Re: Pre-detonation...ugghhh

#5

Post by 65 Eric » Wed Apr 04, 2007 6:17 pm

Thx again Skip, I never thought of asking the dealer, and the price is right. I've done all these other things and at best it's marginal without the hot weather factor. I need this machine to cross hills , plains, and deserts without too much worry. Anyway, I've got about 5 month's to get'er right for the ride to Davenport, WOOO HOOO!!!

see ya,
Eric

Skip
Posts: 231
Joined: Mon Apr 26, 2004 11:18 pm
Bikes: 48 pan
81 shovel
01 softail std
04 heritage
08 roadking
72 ct70
Location: WV

Re: Pre-detonation...ugghhh

#6

Post by Skip » Wed Apr 04, 2007 7:36 pm

I went with the 7.5 to 1 because I was told that what the police motorcycles ran back in the day and with all the parades and idling they did and didn't get too hot I figured what the hell...compression is compression...you only need to go so fast right...My recepit here says the pistons were 48.55 a set and the rings were 26.95....Good luck......Skip

Cotten
Posts: 6911
Joined: Mon Aug 26, 2002 9:09 am
Location: Central Illinois

Re: Pre-detonation...ugghhh

#7

Post by Cotten » Thu Apr 05, 2007 2:20 am

65 Eric!

What does "pinging" sound like?
And when do you hear it?

.....Cotten

65 Eric
Posts: 59
Joined: Fri Jul 13, 2007 10:35 am

Re: Pre-detonation...ugghhh

#8

Post by 65 Eric » Thu Apr 05, 2007 3:04 pm

Mr. Cotten, I hear it only when the motor warms up, and it sounds like the valves are banging around in the head. I have a 65 Chevy six cylinder truck that makes the same noise when it gets hot. It never happens when I ride four miles to work or when I go home, in fact I can't make it "ping" then only after twenty or so miles on the freeway and then only if I roll it on while cruising around 55 or 60mph. If I take off too quick from a stop it will also do it. There was a 48 tooth rear sprocket that I changed to 51 and that helped with getting out the hole without pinging. I'm running single points and STD heads with one plug. Any help is truly appreciated!

Eric

Skip
Posts: 231
Joined: Mon Apr 26, 2004 11:18 pm
Bikes: 48 pan
81 shovel
01 softail std
04 heritage
08 roadking
72 ct70
Location: WV

Re: Pre-detonation...ugghhh

#9

Post by Skip » Thu Apr 05, 2007 3:10 pm

Eric...as you know I am no expert...but...it almost sounds like you need a higher outane gas...well these guys will get it figured out...good luck...........Skip

Cotten
Posts: 6911
Joined: Mon Aug 26, 2002 9:09 am
Location: Central Illinois

Re: Pre-detonation...ugghhh

#10

Post by Cotten » Thu Apr 05, 2007 3:32 pm

Eric!

If if is indeed pre-detonation, it is doing damage.
Or perhaps it is valve lash and a funky cam, changing its song with heat. That could be doing damage too: Particularly if it involves a tappet roller.

My observations with pre-detonation have two points of view:

One is from opening dead soldiers that "never made a noise" (meaning a lot of damage is done without audible hammering),
and then there is my only personal experience, where the old warhorse heavy with hack would literally "clack-clack-clack" when lugged away from a stop.

(This mirrors the conditions used in test engines to determine octane ratings.)

Good gas is hard to find.

....Cotten

65 Eric
Posts: 59
Joined: Fri Jul 13, 2007 10:35 am

Re: Pre-detonation...ugghhh

#11

Post by 65 Eric » Thu Apr 05, 2007 8:38 pm

Thx guys,
Mr. Cotten, "clacking" is probably a little better description than "pinging" and if I don't have the rpm's up when taking off it'll do that. I can buy 100 octane here but that won't help me on the road. I might try some for "diagnostic" purposes but I'm leaning toward changing the pistons to stock compression or like Skip has 7.5 to one. I think stock for mine was 8 or 8.5 to 1. Don't plan on riding in any parades but a parade would pass me on any freeway here in L.A. ! I'll let you guys know what happens.

Eric

mbskeam
Posts: 1004
Joined: Tue Mar 16, 2004 5:52 am
Location: Sultan, WASH
Contact:

Re: Pre-detonation...ugghhh

#12

Post by mbskeam » Fri Apr 06, 2007 4:03 am

well I bet it pings....
STD heads have a 120CC chamber, stock is around 135CC
and with 9.5 pistons and a A grind with a 43deg close time on the intake(this builds more comp)
you can put a stroker cam in, this will "bleed off" some of the compression(latter intake close time)
also retard your ign till it stops most of the pinging, then see with a timing light what you are at.

mbskeam

duoglide58
Posts: 117
Joined: Mon Apr 09, 2007 7:08 pm
Location: Oklahoma City

Re: Pre-detonation...ugghhh

#13

Post by duoglide58 » Fri Apr 06, 2007 4:51 am

When I was running an oil cooler, I found that I was able to run a bit more advanced timing without pinging and got a bit better acceleration. Given the additional heat your setup has you might consider a cooler as additional insurance.
Doug

King
Posts: 387
Joined: Fri Apr 02, 2004 5:05 pm

Re: Pre-detonation...ugghhh

#14

Post by King » Fri Apr 06, 2007 3:19 pm

Mbskeam

Excellent analysis. I wasn't aware of the reduced CCs of the STD heads.

65Eric

Although I agree with Mike that you are pushing the limits of pump gas, here is another factor to consider. Your fresh motor could be developing excessive cylinder temps as the pistons break-in. I got pinging, in situations similar to yours, with my 51FL (STD heads, A cam. 8.5/1 pistons) for the first 15 or so hours of run time after my recent rebuild. I could tell the cylinders were getting very hot.
I followed a club brother's advice and ran the bike for a max of 20 minute rides without any hot starts for the first 15 hours (boring). I also used the Mystery Oil (Ya, I know, I also wave my Hammer of Thor over the bike). With 20 hours on the clock I did a 200-mile club ride, it ran perfectly and no pings since. So, I would wait until you feel sure the motor is broken-in before taking the radical step of replacing the pistons.

Cotten is spot on about gas. I recently got a tank in an "EPA Non-Attainment" area and the bike could barely run on it. I drained it out and put some in my lawnmower and it didn't like it either. Oh for the days of Eythel's 100 octane pump gas, three beer drunks, and firm---- Oops, best not go there.

Great weekend to all.

King

Panacea
Posts: 1857
Joined: Fri May 24, 2002 1:00 am
Bikes: 64FL 99FLHR 01FXSTD
Location: Mpls. MN.

Re: Pre-detonation...ugghhh

#15

Post by Panacea » Sat Apr 07, 2007 2:35 am

Mbskeam, what should we be shooting for on the timing, 35 degrees BTDC? thats where I'm at now. Hoping to get the heads back on soon. Mike

Post Reply

Return to “Motor”