ping at hiway sppeds

[Piston Broke]

Head gasket thickness?

Honest question ... 'received wisdom' is that reducing the squish (by reducing the thickness of base and head gasket and even trimming the cylinders) is good at reducing pinging.

But by how much?

(Not how much squish, but how much does it improve combustion/prevent detonation?).

[JamesButler]

Head gasket thickness?

Honest question ... 'received wisdom' is that reducing the squish (by reducing the thickness of base and head gasket and even trimming the cylinders) is good at reducing pinging.

But by how much?

(Not how much squish, but how much does it improve combustion/prevent detonation?).

Reducing gasket thickness and shaving heads and / or cylinders increases comp ratio, which increases chances of pinging, if engine is not properly tuned to accommodate the increased c.r., i.e., properly adjusted Air Fuel Ratio (re-jetted carb), proper cam, proper ignition timing adjustment (more c.r. requires less timing ignition advance).  In addition, shorter gearing (higher ratio) helps offset (spool off) a higher compression ratio which reduces chances of pinging.

Reducing squish to a minimum of .030" for a modified street motor helps promote a better fuel burn and optimal efficiency, which helps reduce chances of pinging...By how much, I do not know...

[Ironheadmike]

OK folks . I have a Hi4 ignition , Freedom Performance exhaust , Mik HSr42 carb . The  voes  is good , I have no leaks . I timed the bike myself and it is right on . I switched the intermediate from a 45 to a 47.5 (next size up) . The ping has stopped but now it runs flat on acceleration when going through the gears from a stop  . Strange . this carb ran great on my 92 springer with the 45 jet . Which had a complete stage three set up . I understand lugging but 2500 is not lugging .  The detonation is happening when I just roll the throttle just to speed up . like from 60 to 65 or 65 to 70 or even just going up hills .

[Hossamania]

Did you test the voes with a vacuum guage and a meter?

[JamesButler]

OK folks . I have a Hi4 ignition , Freedom Performance exhaust , Mik HSr42 carb . The  voes  is good , I have no leaks . I timed the bike myself and it is right on . I switched the intermediate from a 45 to a 47.5 (next size up) . The ping has stopped but now it runs flat on acceleration when going through the gears from a stop  . Strange . this carb ran great on my 92 springer with the 45 jet . Which had a complete stage three set up . I understand lugging but 2500 is not lugging .  The detonation is happening when I just roll the throttle just to speed up . like from 60 to 65 or 65 to 70 or even just going up hills .

Overall Gearing Ratio for the '92 Springer was 3.37:1...

[Burnout]

You can't control detonation with fuel. You will wind up over-fueled.
You need to back off the timing a little bit at a time until the problem goes away.
The alternative is to use thicker head gaskets, but that will take away squish which helps with detonation .

If you have to a better solution is to use heads that have not been shaved or relieve the chamber to lower compression.

Another consideration is to retard the cam timing so the intake valve closes later to reduce the dynamic C/R.

Take a look at your package and see which area is the culprit instead of trying to band aid it.

[remington007]

You may need to change the setting of the VOES unit. Have you checked the vacuum setting of the switch? IE make it switch to the high load curve sooner. 

[JW113]

You can't control detonation with fuel. You will wind up over-fueled.

Not IF the AFR was too lean in the first place, then more fuel will indeed help. But if not too lean, then yes, more fuel will hurt.

So when I've had this kind of problem in the past, and correcting for everything else, the fix was always: more cam.

Mike, since you have a Hi-4, have you tried dialing the advance delay up to the max?

-JW

[Burnout]

A slower advance curve can help, just taking out a couple of degrees of spark can sometimes solve this depending on the level of detonation present.

Of course a setup cannot be made idiot proof AND deliver maximum performance. You can't just grab a big handful of throttle at low rpm in high gear......

[Hossamania]

What grade of fuel are you running? Have you tried switching brands of fuel?
It could also be caused by a build up of carbon on the pistons.
Has it done this since you got it?
How many miles on the motor?

[Ironheadmike]

I used a multi vac and a multi meter to check  the VOES it turns on just under 5 . I plan on doing some engine work this winter ,but now I want to just ride the damn thing . I'll retard the timing a degree or two tonight when I get home and see what happens .Won't changing the pulleys out mess with your speedo ? I know my 92 had 337 gearing and this on has 292 but still I can't see how getting the rpms up will stop detonation  when it does it at any speed when you just lightly twist the throttle .

[tomfiii]

The voes setting might have to be changed to dresser setting due to weight of model(I see yours is set higher already) as light adding of throttle does not lower vacuum enough to trigger voes,you have to give more throttle or go easier on feeding throttle. I retarded my timing 2 degrees and everything got happy.

[remington007]

I would try a setting 6-7 on the VOES. Reseal the screw if you change it or there will be a vacuum leak.

[Ironheadmike]

I think it's strange that the bike only has 12000 miles on it and it has these problems . Grant it, it sat for 10 years , but the carb sat with gas in it all these years and pitted the hell out of the lower part and the accelerator pump . That is why I'm using the mikuni . I'll put the 45 jet back in ,retard the timing 2 degrees tonight and see what happens . I've been wrenching on these motors  (EVO'S) for over 30 years and this is the first time they have gave me this kind of headache .

[SixShooter14]

Can someone answer a greenhorn question for me?

How does one recognize detonation? Is it obvious?

Just curious. Thanks

[Burnout]

You may have a junky ignition
Check timing on both cylinders?

[Burnout]

Can someone answer a greenhorn question for me?

How does one recognize detonation? Is it obvious?

Just curious. Thanks

Anywhere from a light valve noise to marbles in a mason jar.

[JamesButler]

I'll retard the timing a degree or two tonight when I get home and see what happens.  Won't changing the pulleys out mess with your speedo? I know my 92 had 337 gearing and this on has 292 but still I can't see how getting the rpms up will stop detonation when it does it at any speed when you just lightly twist the throttle .

No, changing the pulleys will not mess with the mechanical speedo. 

IIRC, initially you detonation problem occurred when twisting the throttle in 5th gear at under 2,500 rpm.  Now you're implying that if you're at 3,000 rpm in 5th gear, which is @ 79 mph with 2.925 :1 gearing, and you lightly twist the throttle, then you get some pinging?.  If that's the case, then it seems more like a timing or VOES issue. 

BTW, What exhaust pipes are you using?  How's your oil consumption? If low, maybe a sticky valve not closing properly, causing more heat leading to a ping?

[JW113]

He says it's a 1998. So, electronic speedo. Isn't the sensor for that in the trans? Which means changing pulley, yes will mess up speedo. Unless there is a way to "flash" something to correct it. Sorry, no knowlege of those years Evo speedos.

I think he is saying he's not pegging the throttle in 5th gear, but rather cruising along at 65, and gives it a bit of juice to speed up to 70 or so. And it pings. Been there, done that. Cam....

Mike, I don't recall if you did a cold cranking compression test. Be interesting to see how many psi it pops. That would maybe help diagnose.

-JW

[JamesButler]

He says it's a 1998. So, electronic speedo. Isn't the sensor for that in the trans? Which means changing pulley, yes will mess up speedo. Unless there is a way to "flash" something to correct it.

I think he is saying he's not pegging the throttle in 5th gear, but rather cruising along at 65, and gives it a bit of juice to speed up to 70 or so. And it pings. Been there, done that. Cam....

Mike, I don't recall if you did a cold cranking compression test. Be interesting to see how many psi it pops. That would maybe help diagnose.

-JW

Yes, you are correct re the electronic speedo...he had mentioned a '92 model in an earlier post, and I confused it with his current model. There are aftermarkets who make speedo re-calibrators when pulleys are swapped out.  Baker transmission is one, IIRC...

In my experience with 2.925 :1,  The pinging zone occurred in highest gear as high as 2,800 - 3,000 rpm when cruising then accelerating to pass or climb a hill, and that was with a lighter bike ('99 FXR3). It had a compression bump which was corrected down to @ 9.00 :1 with a mild cam.

However, in the OP's situation, one of his initial posts describes the '98 Heritage Springer as having a stock build, all except for "carb, ignition module and exhaust", so how could the stock cam timing be the culprit?

[JW113]

This is why I was inquiring about the CCP. Just trying to get another data point. Stock cam has pretty short duration, early intake close. So yeah, in a tall gear, probably going to ping in the lower rpms. Even in hot rod form, I fought pinging in the lower rpms as well, and did all the usually tricks like Hi-4 set to longest delay ramp, readjusted VOES for a higher vacuum, etc. All helped somewhat but no real cure. Was on a road trip through Iowa one time, running an S&S 561 cam. Out on the backroads in the midwest, about the only gas we could find was that gasahol crap from these Caseys general stores, which seemed to have driven out every major brand gas station in the state. Bike pinged like a reel of Black Cats at the slightest bit of throttle. Got home, replaced with a Crane High Roller 510, no more problems. Even in 5th. So stock or no, if everything else he inspects checks out OK, and still wants to cruise in 5th below 75, then maybe a cam with a little bit more intake duration might help.

Just sayin'!


-JW

[JamesButler]

This is why I was inquiring about the CCP. Just trying to get another data point. Stock cam has pretty short duration, early intake close. So yeah, in a tall gear, probably going to ping in the lower rpms. Even in hot rod form, I fought pinging in the lower rpms as well, and did all the usually tricks like Hi-4 set to longest delay ramp, readjusted VOES for a higher vacuum, etc. All helped somewhat but no real cure...Even in 5th. So stock or no, if everything else he inspects checks out OK, and still wants to cruise in 5th below 75, then maybe a cam with a little bit more intake duration might help.
Just sayin'!

-JW

Problem with only swapping in a cam with a later intake closing (w/out a compression bump) to a stock Evo is that you are shifting the "power zone" of the bike to the right - meaning the cam "comes on" later i.e., at a higher rpm.  So, if you're preferred riding style is cruising in the mid to high 2000's  rpm, then aren't you just further "dogging down" the bike's performance - kind of like just adding more fuel to the AFR mix and / or  staying with the tallest gearing? 

[JW113]

There's no doubt the torque will go down a little below 2500, though I don't think more than a handfull ft/lbs. That's the effect of bleeding off some of the CCP with more intake valve timing. Not suggesting to put a 262 degree cam in, perhaps somthing with 5-8 more degrees than stock. His '98 probably has the "N" cam, i.e. 30deg ABDC. So, something around 35deg? EV-27?

All a game of trade-offs, no doubt. But pinging, especially sustained, will kill the motor.

-JW

[JamesButler]

There's no doubt the torque will go down a little below 2500, though I don't think more than a handfull ft/lbs. That's the effect of bleeding off some of the CCP with more intake valve timing. Not suggesting to put a 262 degree cam in, perhaps somthing with 5-8 more degrees than stock. His '98 probably has the "N" cam, i.e. 30deg ABDC. So, something around 35deg? EV-27?

All a game of trade-offs, no doubt. But pinging, especially sustained, will kill the motor.

-JW

According to the Mikuni site http://www.mikuni.com/fs-tuning_guide.html (copy & paste), which was referenced in an earlier post, 1º of intake closing is 120 rpm, i.e., the power zone is moves to the right / 120 higher rpm with each added degree of intake closing.  Therefore, swapping from a  30º intake closing cam to a 35º intake closing cam would shift the power zone @ 600rpm higher which provides too much cam and poorer mid-range performance, without any c.r. bump.  The EV-27, which BTW closes at 36º, loves 9.5 :1 mechanical c.r., while stock c.r is a whopping 1-pt lower at 8.5 : 1.

For someone who seems to ride mostly in the mid to high 2000's rpm, not only would he rarely, if ever, feel the "fun factor" of the EV-27 but he'd be feeling less of  a "fun factor" than compared to the dogged stock "N" cam which will at least have some effect in his riding range.  Exactly why I suggested he shorten his gearing to at least @ 3.15 :1, which will serve to definitely move him closer (left) into his cam's rpm power zone and his riding style while also potentially spooling him out of the ping zone...

If anything, instead of swapping in a new cam, why not simply retard the stock "N" by a degree or two?  However with the stock motor, I don't think his pinging problem is a cam timing problem...

I think it's strange that the bike only has 12000 miles on it and it has these problems . Grant it, it sat for 10 years , but the carb sat with gas in it all these years and pitted the hell out of the lower part and the accelerator pump . That is why I'm using the mikuni . I'll put the 45 jet back in ,retard the timing 2 degrees tonight and see what happens.

Just spitballing here, but referencing the highlighted bit of info from one of your prior posts saying that the bike "sat for 10 years", which maybe suggests that you bought this bike pre-owned, recently.  If so, are you sure the Evo is stock?  Maybe heads were shaved by a previous owner and thinner head gasket / base gaskets swapped in to bump up the c.r?  And you're sure the cam is stock?

[JamesButler]