Topic: decel popping

[TwoTired]

However, this isnt the case for the CB650.  They do not have this air cutoff.  Stock exhausts it isnt noticable, but on my 650, there are glasspacks on the oem downpipes.  The bike runs well, but snap that throttle or engine brake, all four with crackle away.  I could tune it to not do it, and for a while I did, but it was so rich on idle, it gave problems cold start and really mucked the idle.

This engine was also a lean burn engine from Honda.  Changing the exhaust has a domino effect.  The air cutoff circuit was tuned for the lean burn engine and part of that design was the exhaust pipe characterization, which you changed.  The domino effect of that meant that the air cutoff circuit also needs to be changed for the pressures the new exhaust now presents.

I suspect you tried tuning other adjustments, which made the bike run too rich at idle, instead of re-tuning the air cutoff circuit to compensate for changes in exhaust back pressure. Of course, Honda didn't make that circuit field tuneable.  But, there are still orifices involved and sizes to consider.

Just saying...

Cheers,

[M.Henry]

It really is a tricky one, the popping side.  Lots of higher detailed answers here, so take this in context with them.  Popping vs backfiring.  Crisp and loud bangbangbang are the bad ones.  This is when you are getting the hard fuel in and it is igniting hard right in pipes.  The valve killers.

The gurgly/rice crispies poppy is more common with open exhausts.  Lack of back pressure and volume means you will hear the gurgling more often and not much can be done.  Like others say, just the leaning out from throttles fully closed.

yeah. This weekend I will be doing some electrical work, putting  a second set of exhaust rings in, and also poking around in the carbs some. Hopefully that will resolve things, but It does indeed sound like it is a popping sound, though I do get some backfires in there too occasionally.

I do have another question of exhaust sounds though. I put in higher compression pistons and I have these drag pipes. I know that the usual way to tell knock (in the absence  of a knock sensor) is to hear it. How should I handle identifying knock issues with the drag pipes?
Should I be concerned with knock on low grade pump gas on 410 pistons and a cork spacer gasket? (I believe I am in the realm of 11.2:1 comp ratio)

[TwoTired]

11.2 : 1 is a pretty steep ratio for pump gas.  Definintely Premium grade is recommended.

However, the cam timing is also relevant. Holding the valve open during the compression stroke, effectively lowers the compression ratio.

Without "hearing" ping, a precursor to detonation, a way to determine risk is by reading the spark plugs.  This is your window into what is happening inside the combustion chambers.  So, read those spark plug tips.

There are other considerations, as well.  A too rich mixture tends to cool the chambers and can ameliorate ping and detonation.  Then there is spark timing to consider, as well. Retarding timing can also be of some help and cool the chambers.  Don't forget, outside temps are a factor as well.  Hot summer temps slow cylinder cooling, leading residual cylinder head temperature rise, allowing the mixture to light off spontaneously instead of waiting for spark to initiate the fuel burn.  Such things can bend rods.  One might select a colder spark plug heat range to help remove heat from the chamber into the cylinder head faster.

There is no doubt that higher compression ratios allow engines to make more power.  But, this usually requires higher octane ratings for the fuel being used to delay spontaneous ignition.

Trade-offs.

Cheers,

[RJ CB450]

However, this isnt the case for the CB650.  They do not have this air cutoff.  Stock exhausts it isnt noticable, but on my 650, there are glasspacks on the oem downpipes.  The bike runs well, but snap that throttle or engine brake, all four with crackle away.  I could tune it to not do it, and for a while I did, but it was so rich on idle, it gave problems cold start and really mucked the idle.

This engine was also a lean burn engine from Honda.  Changing the exhaust has a domino effect.  The air cutoff circuit was tuned for the lean burn engine and part of that design was the exhaust pipe characterization, which you changed.  The domino effect of that meant that the air cutoff circuit also needs to be changed for the pressures the new exhaust now presents.

I suspect you tried tuning other adjustments, which made the bike run too rich at idle, instead of re-tuning the air cutoff circuit to compensate for changes in exhaust back pressure. Of course, Honda didn't make that circuit field tuneable.  But, there are still orifices involved and sizes to consider.

Just saying...

Cheers,

Well, one is limited on what else can be done.  The lack of an air cutoff circuit for the SOHC 650 CVs makes doing any form of adjustment to them rather difficult.

As for 11.2 to 1 compression, that is definitely premium rated.  Even on stock bottom ends, I run the premium in any of my older vehicles.  Though here in Saskatchewan, all premium at the chain stations are 100% ethanol free, which is why I run it.... Well, am sure I get a big blop of gas in the hose that isn't premium if I am at one of them electric select grade pumps.  The though always irking me that I pay for a liter or so of somebody else's regular at premium price and somebody else will get premium bit at discount.

[M.Henry]

yeah the bike had a full tank of low grade that was half a year old, but I rode her enough to need a refill. I threw some premium in. Will ethanol-free premium make much of a difference for the engine temp? I will have to do some spark plug health checks once I get all of my carb and exhaust and electrical resolved this weekend.


Yeah those 410 pistons scared me a lot, so I spend an afternoon measuring volumes and found I was at 13.1:1. I knew that was insanity so I decided to resolve it. I installed a cork gasket at at the base gasket surface which should compress somewhere in teh realm of 0.045". Which puts me somewhere in teh ballpark of 11:1 comp ratio.

[M.Henry]

Well I charged the battery yesterday and this morning it was sitting at 12.6V. Granted I just threw it on the charger and a whiles later I pulled it off. so I don't know for certain if it did full charge. 

Well The electrical gremlins mystery continues.

I rode her some yesterday around the beginning of dusk in my neighborhood. I noticed my headlights, turn signals, and gauge lights were intermittently working. I noticed that they when they weren't working, they would fade back on over a second sometimes when I would hit a bump. Maybe I have a ground short for this portion of my electrical. do they ground to the frame which is grounded to the ground wire through that one engine mount bracket bolt on the right side of the bike near the oil tank? I ask this cause When I was putting my engine in the frame 2 weeks ago, my mechanic partner and I had to fight with the fact that the threaded frame hole for that bracket & bolt was cross threaded. We ended up getting a high grade bolt of the right threads and using it as an impromptu tap to re-tap the threads into the first few turns of the hole which were messed up. then putting the correct bolt back in the hole. I consider that this poor threading that it uses now may result in a bad electrical contact and lead to my electrical issues on why the lights and starter are intermittently working.

[Deltarider]

Is your battery connected firmly enough?

[M.Henry]

It sits in the little slot for it, and it is the right sized battery, but it doesnt have a strap on it to retain it. The wire connectros are screwed in tight though.

[evinrude7]

MH let us know if the exhaust rings do anything.  interested. 

[M.Henry]

MH let us know if the exhaust rings do anything.  interested.

It wont happen till tomorrow evening

Yeahhhh. I'm curious how well it will seal the exhaust since I am going for jank factor of doubling up 2 sets to seal the k7 exhaust to the k3 head.

I am also gonna take the carbs completely apart and probably switch to the recommendations discussed earlier in this thread, as well as re-sync the carbs. I feel like amongst all of that there should certainly be some improvements. Right?

[RJ CB450]

Any electrical intermittancy is almost always a wire issue that can require full going over of the wiring.  Fortunately, not much wiring on these bikes.  I do not think it is the bolt problem.  That is secure and if it was the cause, it would be consistent, not intermittent.

There are two places to check.  It can be a corroded/shorted connector or bad ground.

Before going into any of it though, try and get a wiring diagram copy printed.  Find the problematic component and follow the wires to and from it.  This can sometimes point right away to a connector or another common area, as well as help focus on just what can be potential causes.  A roadmap to diagnosis so to speak.

A voltmeter will be your friend.  Take that light, test resistance to ground, resistance to battery.  You will see one off, or will see nothing.  Resistance is probably bad connector, nothing problematic is usually loose.  Just go through and inspect.  Many a bike has been rendered inoperative thanks to a corroded connector, the killer of rectifiers.

The loose connection, will example my nighthawk.  If it is a bad ground, one thing that can clue that is if neutral vs not in neutral changes the problem (with lights and starting) because in my case, grounding bolt was loose, the one up by the coils.  As result, my lights were instead taking funny wiring path and grounding through the neutral light switch.

[M.Henry]

Yeah I was gonna go through every connection, unplug, dip in dielectric grease, and plug back in securely, then start checking ground connection, then resistances.  Now I don't understand what your saying exactly about neutral. How ever I am noticing that I don't think my clutch sensor is working, because I can not start the bike while holding the clutch in, but rather I have to put it in neutral to start it.

[RJ CB450]

What happens is that the circuit for the neutral switch goes to ground.  What happened with mine is that power essentially flowed "backwards" through the neutral light and groundex via that circuit.  With the neutral switch open, there was no ground.  If you need neutral to start, it could be whatever is the ground for your start switch is open.  For me, that means grabbing an ohmmeter and testing conductivity :x

[M.Henry]

Ok so I put the second set of exhaust gaskets on (2 per pipe) and it still seams like the whole thing is loose.

I guess I should have asked around more before hand, I did try to read around on here,

But is there any major known exhaust leak issues with fitting a k7 (k7,k8,f2) set of pipes to a k3 head (k0-k6)

And if people have been known to do this swap, are there common approaches to resolving this exhaust leak issue?

[M.Henry]

In the mean time I'm gonna go disassemble my carbs.

[M.Henry]

Ok. Update:

The exhaust pipes are loose and dangly some when the exhaust collect is tightened down, so I don't think it's sealing.

The pd carbs are now set to the 2nd up, 4th down clip setting for the needle height. I'm gonna get a jet kit and play around with the pilot and primary jets in the future.

No electrical work so far. My approach is likely gonna be, testing the field coil, individually unplug and plug back in every connector in the headlight housing, then double check the ground in the engine bracket/grounding bolt portion of the ground route.

[Paintedseat]

Mine is running spectacular. Same needle settings as you with a 38 pilot, 115 main. I think yours has 110 stock. I have the idle screws 3/4 turn out. I started with 1.5 out but I was getting a small bog when the accelerator pump kicked in right of idle. It was rich and when the shot of fuel went in it bogged. No more.

[M.Henry]

Yeah. I'm gonna get a jet kit and play around. Yours is a k8 right?
I don't think I set the idle screw right. I put it to 2 turns, then read around some and intended to set it to 1.5 turns but I think I did 2.5.

[M.Henry]

Ok Guys update time:


On the k3 engine in a k7 frame, with k7 4 into 4 drag pipes (essentially no back pressure)
I rebuilt the PD carbs with the needle at 2nd from bottom (with 5th as the stock for orientation) with the idle screws set to 2.5 turns. The jets are still the stock sizes (105 and 40 I believe??)
That left her horribly rich so I rebuilt the carbs again yesterday.

I set her to the middle needle setting and the idle screw set to 1.5 turns. I lightly sanded the spark plugs to give them fresh surfaces for me to see the spark plug health from. I also gaped the spark plugs and set the points gaps all correct while I was doing tune up.

I ran her some and she was fouling the plugs with dry carbon build up when just idling for about 10 mins in the garage. she had a sputter when snapping the throttle instantly from closed to half throttle. She ran well enough though.

When I got on her this morning to commute to university, she wouldn't run on all cylinders. I spent a quick minute and noticed the points gap was a little large some how (maybe I didn't tighten them enough to be vibration proof), and I pulled the 2 outer plugs and noticed that the both had carbon build up and a touch of wet oil to them as well.

So what are y'alls thoughts on what my issues may be?

[M.Henry]

note: I noticed that the threads of the plugs were always wet with a touch of oil on end of the threads closer to the ceramic not the engine chamber end of the threads. I believe this is from an oil leak form not putting in good new rubber nickles in the head. I am wondering if I might be oil fouling the plugs to much from this and also not having new valve seals. If this is the case then I might pull the engine to rebuild all the valvetrain stuff with new rubbers and seals in the near future.

[TwoTired]

I recommend you observe the porcelain insulator at the tips of the spark plug.  When they get a coating of conductive material, like carbon, it doesn't matter how shiny the electrodes are, the spark energy will take the conductive carbon path rather than jump the spark gap.  The carbon essentially shorts out the plug.  During the build up of carbon, misfires become intermittent.  It's futile to tune a motor with fouled, contaminated spark plugs.
Not uncommon for a sputter to occur with fouled spark plugs.  Get a new set of plugs, or torch the tips clean of any fouling of the insulators.

The slide needle and main jet has minimal effect on idle mixture.

I haven't re-read this entire thread, but I must mention that sooty plugs CAN be the result of float chambers overflowing.  Essentially dumping raw gas into the carb throats that can't be burned off with available oxygen.   Have you checked the actual fuel level in the carb bowls?   Adjusting jet orifice size is futile if the fuel levels aren't where they should be.

The only thing in the head that can let oil into the cylinder are the exhaust guide valve seals, and/or excessive clearance between valve stem and head, or a cracked head.  Oil at the base of the spark plug (outside the chamber) isn't going to get into the chamber to foul spark plug tips without also losing a lot of cylinder pressure during the combustion.  In general, oil on the outside isn't going to get at a spark plug tip inside the combustion chamber.

Also note that oiling the spark plug threads is ok for cast iron heads, but not aluminum ones.  The high heat eventually cooks the oil and turns it into glue.  Then removal of the spark plug also removes the aluminum threads in the head.

Cheers,

[RJ CB450]

What one can use is an ultra high temp anti corrosive like a silvercote.  Good for temps higher than the melting point of aluminum.  I use it on exhaust studs especially to keep them from rusting and siezing up

https://www.permatex.com/products/lubricants/specialty-lubricants-anti-seize/permatex-anti-seize-lubricant-2/

[Paintedseat]

The stock idle jets are 35. If you have 40s and you are 1.5 turns out you are way way too rich at idle. I have 38s and I found the best adjustment is 3/4 out. I am even going to try 1/2 out.

[M.Henry]

I have not done any jet changing and don't intend to. I have heard on this forumn that the PD carbs have enough adjustments built in that it is prossible to tune it without re-jetting.

I will torch my plugs (I assume you mean I can use my propane torch and hold them in the flame for a few seconds) to clean the carbon off. I definitely need to resolve the carbon buildup on the plugs first so I can then see the other indications of the ceramic coloring.

I'll throw some high temp Anti-Sieze on the threads from now on just in case. thanks for the pointer.

Sid enote: I ran a compression checker on the two outside cylinders this weekend and got 150 PSI and 180 PSI. That is more then a 10% increase  so do I need to look into that?

[M.Henry]

so with the #35 idle jets. What am I going to be looking at for setting that x/x turns out? would I get clean plugs and put them in a hot engine, then turn the bike on and sit it at idle for 10 mins then pull the plugs and investigate?