Topic: Another satisfying ride!

[HondaMan]

It's so much fun    to debug and fine-tune these bikes after a full teardown-rebuild....today I had the first chance to ride it outside of city/freeway commuter traffic since the full rebuild in 2013 (yep, been buried with work nonstop since then   ). I rode from Denver to the top of Mt. Evans, the highest paved hiway in the country (the sign in the middle of the climb says "..the world.."      ) thru sunshine and heat, rain, snow, hail, 50+ MPH winds, and fog. That ought to cover it...this was the first chance to fully test it up to 100 MPH in all situations.

A couple of interesting findings: when getting onto the big climb (7%+ grades) at Colorado-like freeway speeds (80-90 MPH), a 1-year-old Harley behind me couldn't keep up. That was different: he gave up about 4 miles into the climb when I dropped into 4th to jump up over 85 to beat a line of cars to a narrowing lane at the steepest point. I've geared the bike too tall for this mountain work, I'm afraid, but it sure likes it on the downhill parts.

I've also discovered the OEM rear sprocket is not concentric.   At speeds over 80 on steep grades there is a surging vibration coming from the driveline, and a dial indicator on the recessed ridge of the sprocket is showing more than 0.6mm out-of-round, while the width of the grooved ridge is identical at all points (relative to the tips of the teeth). This was an NOS Honda sprocket off eBay from some shop in Arkansas 2 years ago: I think it might have rather been a returned unit from [many] years ago that ended up in someone's warehouse and was sent out again as "new" because to the naked eye, it looks fine. The center hole and the 2 stud holes I measured are exactly distanced from the recessed groove, so the center hole itself is what is at fault. I will have to take it off the bike to verify this, though. Rats, I thought I had a "rare find" there.

Also: above 12000 feet, the DPR8EA9 (NGK) sparkplug idles better than the X24ES-U or DR8ES-L plugs I have used before. For you other 'mountaineers' out there, maybe this will help? I'm currently using OEM coils (new 2 years ago), but will switch back to Sakura coils (from PartsNmore) this winter to test them with this plug. I previously used the X24ES-U, DR8ES-L and XR24ES-U plugs with the Sakura coils and found better cold starting and stronger idle on hot days (with ethanol-laced fuels) than with the OEM coils. But, I didn't try the DPR8EA9 with those coils.

[Jerry Rxman Griffin aka MuthaF'er]

Good ride! About time you were able to just go enjoy yourself.

[mrbreeze]

Hey Mark, Any jetting changes along the way? You're talkin' some serious altitude. What are you starting off with at the mile high? Back in the 80's me & the lady took a trip from Calif. through to Wyoming and on down into Colorado. We took 70 back to Calif. and I remember going on Eisenhower pass waaaay up in the sky. Of course that was in a fuel injected car so no probs. with the altitude change. I'm talking about main jet changes and maybe even fiddling with the air screws and such.

[HondaMan]

Hey Mark, Any jetting changes along the way? You're talkin' some serious altitude. What are you starting off with at the mile high? Back in the 80's me & the lady took a trip from Calif. through to Wyoming and on down into Colorado. We took 70 back to Calif. and I remember going on Eisenhower pass waaaay up in the sky. Of course that was in a fuel injected car so no probs. with the altitude change. I'm talking about main jet changes and maybe even fiddling with the air screws and such.

It does start losing some power above 8000 feet, more noticeable above 10,000. I just keep the revs up, and it does fine. The situation this time was: I had installed a 19T front chain sprocket on it to tame myself in commuting after I surprised myself with the extra power I got from this last rebuild. I was 'riding by reflex', having this bike 40+ years, and kept finding myself WAY too fast, so I geared it up until I [re]learn to behave myself...but in the hills, this meant I spent most of the time in very low gears to keep the revs high. In fact, the stretch between Summit Lake and the top I was in 1st the entire way but for a short stretch, running their silly (for bikes) 20 MPH uphill speed limit. I never got to 3rd gear on the entire mountain!

The early carbs (pre-PD type) start running lean at half throttle, if jetting is spot-on below that. Mine is set slightly wet at #108 mainjets (it came new with #110, like most K1 engines) and if I do it next year I'll probably opt for #105 if the traffic is less? This time there must have been 3000 cars on it between the Lake and the peak! Labor Day...

Generally, I run the #108 where I live (6000 feet) and in commuting. If I head back East for something, or to Texas (work, usually) I sometimes drop in the #110 again, but run less octane as the altitude increases. For the trip up the mountain this time, with #108 inside, I ran midgrade despite the 9.2 CR it now sports. The whole idea was to test it with the new plugs, slightly higher CR, and feel the new power put to work on the I-70 fast lane up the hill. It was worth it! I broke into a smile when the HD dropped back off...   They can really rip to about 70 MPH up here, then their show is over, it seems. If I had, at that moment, gone to regular grade fuel (85 octane here), I would have REALLY ripped up the hill! As it was, I just broke 92 on the top of the 7% grade at 9500 feet in 4th before I ran out of road and could smell unburned fuel wafting back from behind the Vetter.    That's certainly better than it was before I started all this stuff, where I pulled that at 70+ the last time I tried it.

RXman: how is the monster bike? I haven't seen it in ages, since you got the head back from MRieck.

[RAFster122s]

Mark, Given your experiences with the 750 rebuild...so, care to share your gearing?  So, any guesses at "normal"...wait, that sounds bad ... altitude would these recommendations for plugs be the same?
Care to point us to your rebuild summary in that thread.

(Bad thing about the site is you can't easily go see threads you have watched...or if you can I don't know how...other than those you have participated in by posting. Then you can go through your posts from your Profile page to find that elusive, reclusive posting to find the thread title where you can pop into the thread.  Provided you have a clue as to the name of the original thread.

There's no 750 in my "camp" and probably won't be...for a 550, care to share  any contextual changes to your previous recommendations for plugs and similar that could transfer over to the smaller bike? I'm looking at one that is pretty much stock or one that is with 650 cam with just easy and quick changes*. 
 *(Including a very simple clean up of intake port matching to intake header & any boots and the screw ends which may be in the intake tract, etc.)
Granted, you have documented the "breathing on it" head porting recommendations in one of your recommended head modification threads to improve power, etc.)

Currently looking at stock coils with new copper core wires cut into the coil body with epoxy and RTV to seal the surgery. BTW, the NGK coil wire splices work well but, they are are kind of big and clunky. Coil wires on the 550 coils I am dealing with are very short and have to be changed for added length and to replace aging wire. I need to check the secondary coil resistance readings to see if they are out of whack and coils need changed before going to trouble of cutting into them.  When you have time but no money, you do what you have to make things work.
Thanks!
September all ready!  Spells snow around the corner for the Rockies high elevations...provided it starts to cool down (Been a hot summer here)
David

[becken]

Mark, I noticed you are using a resistor spark plug that is designed for a wider gap. Are you still using resistor caps and gapping to .028, or are you using high output coils? Basically, did you change anything from stock to be able to use these spark plugs?

[HondaMan]

Mark, I noticed you are using a resistor spark plug that is designed for a wider gap. Are you still using resistor caps and gapping to .028, or are you using high output coils? Basically, did you change anything from stock to be able to use these spark plugs?

I like the DPR plugs for 2 reasons: they have a very extended tip (into the chambers) and they are resistor type, at the same heat range as the D8EA. I would like them even more if ND would make a version in the "Hot U" series, maybe they will? The "Hot U" plugs are all about 1/4 to 1/2 heatrange hotter than the 7 or 8 (respectively) NGK versions, which these bikes appreciate. My coils are presently OEM units (new in 2013), but I have and will re-install some Sakura coils from PartsNmore. I used them last year for a while, and they closely match the ones Honda used in the post-1975 750 and the 500/550 bikes, but have about 800 volts more spark overall. The duration is very close, if not exactly, the same as the OEM coils. Adding some resistance to both the cap and plugs makes it close to Honda's original design: the bikes before 1974 had 7500 ohm plug caps and 10,000 ohms after that. The 5000 ohm plug caps we mostly find now come up short, so using a 2000 ohm sparkplug puts things closer to the original design. Since I haven't found the [imaginary] ND version of this plug yet, I don't know what their resistance might be?

[HondaMan]

Mark, Given your experiences with the 750 rebuild...so, care to share your gearing?  So, any guesses at "normal"...wait, that sounds bad ... altitude would these recommendations for plugs be the same?
Care to point us to your rebuild summary in that thread.

(Bad thing about the site is you can't easily go see threads you have watched...or if you can I don't know how...other than those you have participated in by posting. Then you can go through your posts from your Profile page to find that elusive, reclusive posting to find the thread title where you can pop into the thread.  Provided you have a clue as to the name of the original thread.

There's no 750 in my "camp" and probably won't be...for a 550, care to share  any contextual changes to your previous recommendations for plugs and similar that could transfer over to the smaller bike? I'm looking at one that is pretty much stock or one that is with 650 cam with just easy and quick changes*. 
 *(Including a very simple clean up of intake port matching to intake header & any boots and the screw ends which may be in the intake tract, etc.)
Granted, you have documented the "breathing on it" head porting recommendations in one of your recommended head modification threads to improve power, etc.)

Currently looking at stock coils with new copper core wires cut into the coil body with epoxy and RTV to seal the surgery. BTW, the NGK coil wire splices work well but, they are are kind of big and clunky. Coil wires on the 550 coils I am dealing with are very short and have to be changed for added length and to replace aging wire. I need to check the secondary coil resistance readings to see if they are out of whack and coils need changed before going to trouble of cutting into them.  When you have time but no money, you do what you have to make things work.
Thanks!
September all ready!  Spells snow around the corner for the Rockies high elevations...provided it starts to cool down (Been a hot summer here)
David

The "rules" for the spark systems on these bikes are all the same: they break down into the pre-1975 and post-1975 versions.
In the pre-1975 they all had the same coils (except the 500-4 and 550), 4.5 ohm primaries with 7.5kV spark at 1.50mS duration, running 7500 ohm plug caps and non-resistor plugs. The post-1974 versions had 4.3 ohm primary coils with 8.0kV spark at 1.42-ish mS duration and 10,000 ohm plug caps on non-resistor plugs (except in Canada, where they came with resistor plugs, too).

What you want is: the longest-duration spark you can get. The engine needs only about 4500 volts to spark and run well, and most "high output" coils trade off spark duration (very short) to get higher voltages, which simply are not needed. In truth, if you plunk in a set of, say, Dyna 3-ohm coils (not for the bikes smaller than 750, though) and it improves something, then something else is wrong. Usually, this amounts to burned-out sparkplug caps, or maybe bad connections in the bike's wiring, but the riders are seldom aware of this issue. Having real high resistance (more than 12000 ohms) in a burned-out cap will then extend the duration of a higher-output coil by delaying the discharge after it actually jumps TWO gaps: one is the burned-out resistor and the other is the plug itself.

The main thing I find today is: the enamel coating on the wiring inside the old coils is flaking off and the output windings are shorting out. This reduces both voltage and duration, and makes them run hot (and eat points). They were designed for 10-year life, so it's not a surprise? The Sakura coils are only $80 per set and drop right in if you don't mind oddball wire colors (Honda's are $150-ish for the entire bracketed set), and seem to be good quality. And, they have REAL long spark wires!

[becken]

Mark, your information is always right on and you always make it very understandable. Thank you for being willing to share it with us.

[RAFster122s]

Thank you Mark for the detailed and succinct description. I am glad you have an excellent memory and are a very good engineer, evidenced by your breadth of knowledge and methodical and logical replies and posts.

I get buried in the details sometimes.

Thanks again!
Has  the SOHC/4 boards started making holidays celebrating and recognizing the brain trusts we have here?  You know, its HondaMan Day and it ain't your birthday... 

David