Verify my compression numbers are right

Hey guys - finally got around to doing the comp test.

Did a nearly cold test - had cooled off for about 2 hours.

Numbers:

1 & 4 were ~ 160PSI
2 & 3 were ~ 150PSI

After warming up the motor, rechecked:

All 4 cylinders across the board went up 1-4 PSI max.

The highest cylinder was #4, @ 160PSI, 160 after warm.

I know they are not LOW numbers at all, but are they too HIGH?
I know too high is a problem somewhere, but I forget.
But they seem good to me, please verify my results!

Thanks guys.

 

Standard 156
Minimum 128
Maximum 171

Max diff between cylinders 14

Sounds like you have great compression.

 

Did you shave the head? Have you run a little rich for a while? Either condition will bring those numbers up. The former is expected, the latter, not so good. Carbon buildup in the chamber can lead to hot spots, predetonation and cracked heads/burned pistons. Given that you are close to the high end (156psi max), I'd be concerned as well. What color are your spark plugs?

 

I have been running rich.

I just did a colortune w/o YICS to get the mixtures at least firing all the time at idle. Then put the YICS in, sync'd, and now I am ready for a final colortune again.

I did take a run around the block @ 3 turns out, when it used to run good at 6 turns. Idled like crap. Got it back, pull the plugs - #3 plug was TOUCHING the anode. WHAT THE HECK?!

Also mashed my plug hole threads a bit, but I kroiled them and they are a bit better. (only one hole)

Robert, you said 156 max, Bill says 171. What's right?

Carbon buildup is gone. Used to be a lot. When I did the comp test, it was gone. If I was getting predetonation, would I hear it?
If I was hurting my cylinders, could I see it? I have inspected visually my crowns they look nice and clean, even the etched symbols on the top are good.

So - The sync I just did, along with richening the 3 turn out setting to about 5, or so, really cleaned up the idle.

I think the run around the block real lean might have melted my plug tip on #3 so it bent closed? Is this possible?

 

DP, no expert, just opinion. What does your manual say the cold cranking pressure should be for your model? Do you always hold the throttle wide open when you crank it on each cylinder? The numbers you posted aren't that high for a modern motorcycle and a stock Harley runs around 150#. People run regular gas with CCPs around 170-180# so yours sounds good.

As for the side electrode touching the center electrode on your plug, something bumped it good or it was improperly gapped to begin with. Put another properly gapped plug in that cylinder crank it over for a second or two, pull the plug and stare at it. If the side electrode is again bent in to the center electrode, you have an obstruction on the top of that piston.

Your combustion chambers aren't going to get nearly hot enough to fry that electrode and somehow force it into the enter electrode. If it got that hot, you would have see-thru pistons already. I suspect the plug was improperly gapped or you bumped it against something putting it in.

Don't confuse pre-ignition with detonation. Pre-ignition is caused by a hot spot glowing in your combustion chamber and firing the mixture ahead of time.

Detonation is spontaneous combustion from high pressure, heat, cheap gas and your CCP numbers aren't way up there. I don't think your timing could be that far off (could it ???) and you'd hear a light knocking/pinging noise as you really get on it hard. The noise speeds up with RPM. If you're hearing that noise maybe your timing is way off.

 

My timing chain has never been checked for adjustment - mostly because I don't know what tool to get in there and loosen the nut etc.

I had a light noise between 1500 and 2000 the other day, but I think it is gone now.

I threw another plug in, gapped to 0.028 and it went in, fired up, and came out 30 seconds later, and it's fine... Maybe I just nailed it dropping the plug into the hole on the corner of the hole or something last time.

Idle seems better with new sync. Definately.

 

You have to take-off the Cam Cover and LIFT the Chain UP Off the Cam Chain Bridge to chech for SLACK.

The Chain shouldn't want to move at all. It should be nice and tight. If you can lift it off the Bridge you need to Adjust the Tension ... -Or- If the Tensioner is at the Limit ... the Chain.

Chains are usually good for 55,000 - 60,000 Miles.

 

Timing chain effects camshaft timing adn I don't believe that's your problem, DP. Your ignition timing (whole different animal) could be off. You might want to whip out the manual and check that since if it is too far advanced you can get detonation.

If you lug it down to 1500 - 2000 in too high of a gear, you could get the sound of detonation in a pretty good running bike engine. The cure for that kind of "detonation" is simply to drop down a gear. :wink:

I think your numbers are just fine and if the bike isn't running to suit you, the carbs might need a little more fine tuning or cleaning. Throw some Seafoam in the tank, ride it and see what happens.

 

My numbers are from the Haynes manual. The service manual only specifies 156 as the normal pressure. By the way these are always stated as at sea level.

 

Gee Bill, I pulled mine off of a 81 Service Data Sheet...for a 750...DOH! I gotta pay attention.
I pulled my Haynes off the shelf and confirmed your numbers off of page 37.
From the sounds of it Dpawl, you are in good shape!
Now I'm left to wonder if the specs on the Data Sheet are in error given the Haynes spec. I'm in agreement with Icantinaturner's logic. I'm gonna have to run a check on my 750...

 

Doug. Settle down. Your compression numbers are fine. Finish tuning the bike. RIDE IT. That was the whole idea in the first place. You've succeeded. Now go for a ride.

 

agreed.

 

I can't.

its running terrible again.

bogging etc.

how often does the cam chain need to be tightened? its a lot noisier lately, I think I may have stretched the chain a bit after riding real hard. the old owner rode it very easy. once I got the power back, I ran hard and probably shouldn't have. its chugging with low rpm and feels held back after that.

the mix screws are still way out, but its the only way I can get the colortune to fire without missing. 3 turns out and it was barely firing.

the sparks look weaker than before... this thing is driving me mad. seriously.

 

Chain self adjusts - the hand adjust process should not be required very often at all.

Your other issues still sound like you have some tuning to do. It's frustrating until you get it right. It is an iterative process. Tune, sync tune, sync etc.

Take a step back and relax - then jump back in.

 

Sync twice... tune 4 or 5 times.

Tune via colortune.
Colortune stays nearly blue the whole time.
But it DOES react. It changes as I move it, on all 4, exactly the same.

So my ports are not clogged - unless they are ALL clogged, EXACTLY the same amount, and none are completely clogged... because they all react, and react the same.

It's definately not right. Nobody on here has any clue WHY my bike runs pretty damn good @ 6 turns out on the mixture screws. Nobody can figure it out.

With the screws 3 turns out, it barely fires and runs real rough idling.

When I got the bike, the screws were that far out- figured brand new EVERYTHING in the carbs, fresh plugs, check for leaks, valve clearance adjustment, new valve cover... blah blah blah... would fix it. Nope. Not at all.

No way in hell it's running like this because the oil is nasty right?
I mean, there was a lot of carbon in the cylinders, and it's all gone now that it's been run a lot.

Still don't see oil causing it to run like that... ugh.

Piece of crap... errr.

 

i think that when there's no carbon on the cylinders that it means it's lean. I could be wrong, but i thought i read that somewhere.

 

You are gonna hate this answer - are you SURE you have your carbs surgically clean? (told you you would hate it)

Seems if you have it open that far some air or fuel passage has to be partially clogged. Or since you see it on all 4 could a jet be wrong or swapped? Got to be a reason here...

 

lol, i don't hate the answer, but i'm sure he will.

 

You DON'T adjust the Mixture Screws: "Turns, guarter-turns, etc."

You ADJUST the Fine Tuning a matter of DEGREES.

 

One Chance at Redemption.

You don't know what's-what because you are not doing the "Tune ONE Thing At A Time" Universal Rule of Fine Tuning.

Tune ONE thing. Observe results.
Tune More than One thing. You don't know what you did that altered the results.

So.
Let's eliminate ONE thing.
Mixtures.

Buy an Accurate Mechanics Ruler
Set the Depths of the Piot Mixture Screws to --> Precisely 27/100ths of 1-Inch Deep.
The Wings ... Not the Slot bottom.
Set the Wings on the Pilot Mixture Screws to: 27/100ths ... 27 ... Not 26 or 28 ... Get it On-the-money.

Test the Bike with Pilot Mixture Screws set to that DEPTH as measured form the FLAT Top of the Carb Body above the Screw.

Maybe we can find-out if your PROBLEM is something OTHER than the FUEL Part of the Ratio.

 

fine tuning? far cry from that.
after two good syncs... drop in colortune. ALL 4 cylinders do the EXACT same thing. 3 turns out there is barely any visible combustion.

turn out 8 degrees- I get no response. takes over 2 turns to start reacting. then it stops being spuratic with firing, and starts firing with every spark.

at this point I am 5 to 6 turns out, just to get it to burn every spark.

all 4 cyl's like that.

ran great all afternoon, just a little noisy motor (cam chain?) which started a week or so ago.

my spark looked weak in the colortune. is it possible its so weak it needs the mixtures much heavier on the gas side of the mix to burn better?

 

just ran 1/4 can seafoam in my fresh tank... only 12 miles in the tank and I felt more/even power on the highway. got off highway - running smoother.
idle went UP 150 rpm. tweaked back down to 1050 and its idling better than ever. nice and even, no skips or hiccups.

is it seriously possible... 12 miles with seafoam and its showing signs of cleaning up? or am I just losing my mind hoping for it to get better? it felt good to hear that idle not missing a beat.

 

Ran a 1/4 bottle to a full tank through the 82 Seca today... yup, it's that good. My buddy got his R1 out of hybernation (10 months!) and fired it right up (with a new battery). I shared my can of Seafoam with him for today's ride. Lake Castaic is rather nice and the weather was perfect.

 

Vegas odds are currently bid 5-to-2 on mind loss.

Of course, if you're right, then we really didn't get our carbs zestfully clean, now did we?

 

If it runs right at 6 turns out so be it.
Don't sweat the small stuff.

 

Len's right you know, if SeaFoam is making a difference, SOMETHING in the fuel system wasn't "zestfully clean." This is good news though; give it a chance to work and you may be able to get the carbs adjusted correctly yet.

 

Me too :lol: ( told you you would hate my answer but this seems to be backing it up)

 

The Pilot Mixture Screw regulates the flow of AIR from the Pilot AIR Jet into the Combustion Chamber through a TINY Inlet in the Carb Intake inside of the Throttle Plate. The Pilot AIR Passage is married to the Pilot FUEL Jet Supply by a Passage connecting the AIR and Fuel Supply.

As the AIR Supply is INCREASED the FLOW Siphons FUEL from the Pilot FUEL Jet Supply and the COMBINED MIXTURE is Delivered to the Cylinder to allow a Pilot Mixture to support IDLE and OFF Idle performance.

The FUEL Supply is Regulated by the SIZE of the Pilot FUEL Jet.
The AIR Supply is Regulated by the SIZE of the Pilot AIR Jet.
The FLOW allowed to Enter the INTAKE Manifold is regulated by the Pilot Mixture Screw.
The FLOW. NOT the Mixture. The Mixture is dependent on the Size of the FUEL and AIR Jets.

As the Pilot Mixture Screw is Turned OUT from Bottom to INCREASE the FLOW ... there is an initial distance of the Pilot Mixture Screw being LIFTED and Opening the Passage to the Combustion Chamber where ONLY AIR is Supplied to the Cylinder ... the Vacuum force upon the OPENING Pilot Mixture Screw Opening NOT opened enough to allow FUEL to be siphoned from the Pilot Fuel Jet Supply.

As the Pilot Mixture Screw is Lifted (Turned Out) the FLOW is allowed to INCREASE and the Pilot AIR Supply Siphons (Draws-up) FUEL from the FUEL Supply regulated by the Pilot FUEL Jet.
(If the JET or the Passage is clogged ... the Process DOES NOT occur)

Eventually ... (Depending on the Condition of EACH Separate Cylinder's strength of VACUUM Created during the Intake Stroke) ... the FLOW of Pilot AIR will INCREASE causing the AIR to "Suck-up" some FUEL from the Pilot FUEL Jet Supply.

As the Pilot Mixture Screw is Turned OUT and the AIR begins to Include FUEL the PILOT Air~Fuel Ratio suddenly goes from ZERO Fuel to "Containing" Fuel.
The FLOW is not at Full Strength so the FUEL included is LEAN.

As the Pilot Mixture Screw is further Turned-Out ... the FLOW of Pilot AIR Increases and likewise Siphons an Increased Amount of Pilot JET Fuel.
The Air~Fuel Ratio changes.
More FUEL accompanies a Slightly Increased AIR Flow.

Then, the Point where the Pilot Mixture Screw is Turned-Out allowing the Maximum Amount of AIR to be drawn-in through the Pilot Air~Fuel Orifice is reached. This AIR draws FUEL from the Pilot FUEL Jet as before.
The Pilot Mixture Screw is WIDE Open.
NO further adjustment OUT has any effect.

 

Thanks guys.

And Rick- that was a great description of how the pilot screw works.

You should sticky it

So if my passages were ALL PARTIALLY clogged... this would be the case, correct?

Riddle me this, Batman...
So many people on here talk about the screw affecting idle and off idle performance.

Yet - I have heard from the grapevine, of significant person, that it affects.

Now, from what I can see most everyone here denies that, saying it shuts off flow between 2000~3000.

OK, sure.

Now, remember to get that 'tan' color on the plugs, it takes a bit of riding. OFF IDLE riding. Above 3k.

When you check the plugs, and they are rich or lean, you adjust the mixture screw. BUT WHHHHYYY oh WHYYY, batman!?

I thought off idle, they didn't affect anything???

So Batman, where do we lie?

'PILOT SCREW' only affects below 3000... yet we use that to color the plugs, ABOVE 3000. Does that make any sense, Dark Knight?

If any of you want to step in and help out the Batman... please do!

 

When the Pilot Mixture Screw is Turned OUT ... the Flow INCREASES.
To a point where you set it.
If you set it to Make the Bike Idle .... the Bike runs.

If you set it to make the Bike Idle ... and ADD a little MORE Flow ...
The Bike Idles and Transitions from Idle to Off Idle without difficulty.
Too little Flow ... No Good. Backfire; hesitation waiting for Main Jet Fuel.

Too Much Flow ... No Good. Bogging-Out because there is too much Fuel ahead of the Main Jet Supply.

The Pilot Mixture Screws Supply is ALWAYS Present.
It supplements Main Jet Supply.
Main Jet Supply + Pilot Mixture Supply = Total Mixture

Main Jet Supply + Lean Pilot Mixture = Too Lean of Total mixture = Plugs too Light from not enough Fuel
Main Jet Supply + Adjusted Well Pilot Mixture = Tuned Total Mixture = Plugs Colorized according to Supplemental Pilot Mixture.

 

Awww... Rick beat me to it.

 

So what's all the BS about pilot mixtures null and void after 2-3k?

Heard a LOTTTT more people saying that, than what you just said Rick.

Personally, I believe you 100% on that notion. That's what I would say.

I just don't get why people say it dies off... I can see it obviously being confused, as in the mixture is still present but not the main source of fuel.

Lots of folks on here need to be a bit more descriptive, like not saying your pilot circuit is 'off' after 2-3k. I was thinking if that were the case, the air volume passing through the carb might be high enough to essentially block off the pilot mixture holes. But in reality - it's causing even more 'suction' out of it, right? But it's limited to so much air/fuel via the jets... so the increased suction won't allow it any more of either.

So Rick, what do you think about 6 turns out? Does that mean my carbs aren't clean enough, but they are not clogged either? Makes sense to me.

Remember - I know about the 8 degrees of fine tuning thing - but I am not close enough for that. Like I said, colortune shows blue across the board really. Light hints of yellow. Essentially, hard to get it 'rich'. So that would help show that my plugs are indeed showing lean, also explain the rough idle... and as the carbs (hopefully) clean up more with the fuel/seafoam... they should slowly turn into rich plugs, and I will have to dial in my screws.

Sound like a plan?

 

Doug I asked the same thing a while back.The answer I got is the Pilot contribution becomes negligible once the main opens. But my argument has always been then why does it effect plug chops at higher RPM. I dropped the subject. I'm glad to see Rick confirming what I thought. The contribution while minor still has enough of an effect to get rich or lean mixes at running RPMs

Rick thanks for the clarification! I always knew there was no shut off but could not refute the negligible part except that plugs change color...

 

The Mixture is dependent upon the Pilot AIR Flow and the Amount of FUEL present in the Pilot Fuel Passage to be drawn-in.

When the Screw is Wide Open ... you need:
Sufficient AIR through the Passages
Correct Quantity of FUEL Metered by FUEL Jets.

If the AIR Jet is Wrong ... the process fails ... Check AIR Jet and Passage.
If the FUEL Jet is Wrong ... the process fails ... Know Size of FUEL Jet and that Pilot FUEL Passage is clear.
If the Pilot Mixture Screws are Incorrect ... the Process suffers.

Pilot Mixture Jets are Tapered or Shouldered.
You need the right ones.

Common Mistakes;

Wrong Pilot FUEL Jet. Tuning error.
Pilot and Main AIR Jets reversed. (Haynes misprint)
O-ring & Washer Flop. (O-ring blocks passage. No Fuel or Lean)
Wrong Mixture Screws. (From different Carbs replacing drilled out Screws)

 

Hmm. Got me thinkin' bout the oring/washer flop. I'll have to check that.

 

I agree with what has been said.
As stated the mixture screws contribute a minor amount after 3000rpm in comparison to the main jets.
And as stated there comes a point when the mixture screw is all the way out.
They can make it no richer.
This is were the rejettting comes in.

 

Alright... I'll do it. :lol:

I claim that the pilot screw shouldn't affect anything except at idle. Not even the off-idle transition. 8O There. I said it.

It's off the original topic here though and I suspect it's gonna get a little messy, so I started a thread specifically to talk about it:

http://www.xjbikes.com/Forums/viewtopic/p=153711.html

Burnarr

 

I know, I've been following it. I do believe that the screws affect your mixture across the board though. The constant velocity of air running through the carb body is going to constantly suck fuel out of that port...

I believe that 'minor' amount is what makes the plugs tan, white, or black.

Think about it, if the main supplies 98% of the fuel... then the 2% missing is the bad mixture... too much air, not enough fuel. 2% shy of fuel.

That screw allows the 2% to come into play.

With the jetting correct on the bike, ie stock... and the idle set properly, those main jets should allow for proper fuel mixture WHEN the pilot mixture is set properly.

If you rejet to tune the high RPM/throttle plug chops... and get it dead on, with your screw ALL the way in (closed) then you are going to not have enough fuel to idle properly.

Then when you OPEN that screw to let fuel in for idle, and get the idle set - your jets are letting too much gas in. That 2% + 98% that is set at factory, is now 2% plus 100%, 102% total.... and that 2% extra fuel will show up as rich on the plugs.

Make sense right?

Granted - my 'numbers' are just mere guesses, it could be closer to 0.5% and 99.5% but I don't know that much about it.

But do you see where I am coming from?

I can't see SO many people tweaking those screws, SEEING colors on plugs change at high RPM chops... and still believe that the screw 'doesn't affect anything but idle'.


On topic for my problems... I am pulling my pilot screws out today to indeed see if Rick might have something going here... if my orings/washers are flip flopped, that could be my problem.

What is the proper way for them to sit?

I have to admit - when I installed mine, I just left them the way I took them out. It could have been wrong.