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Author Topic: '58 RE Indian MPS-750-PF Build  (Read 21303 times)
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Scottie J
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« Reply #90 on: February 11, 2015, 09:42:59 PM »

Plug chops.  But I hope to have it on the dyno this summer and put a sniffer on it.
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fordboy628
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« Reply #91 on: February 12, 2015, 07:26:02 AM »

Plug chops.  But I hope to have it on the dyno this summer and put a sniffer on it.

Clean spark plug cuts are the tried and true method most racers/tuners use to evaluate internal combustion chamber conditions.    It works great, as long as you know how to read plugs for detonation and pre-ignition.   It also helps to patiently adjust your "tune-up" in small increments.

My experience is that you can survive a "toe" over the line, but a "foot" over, kills your engine . . . . .
 cheers
Fordboy
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Scottie J
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« Reply #92 on: February 12, 2015, 09:10:27 AM »

This pic isn't from actual chops, but this is the overall burn from my 20 minute ride at between 1/8 and 1/2 throttle.

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fordboy628
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« Reply #93 on: February 12, 2015, 09:39:57 AM »

I looked at the original pic on photobucket but I can't see enough detail to say anything, except that there seems to be a small difference in mixture strength and/or oil consumption between the cylinders.

Beg, borrow or buy a Champion, lighted spark plug viewer with magnification.     It's the best way to read plugs, and the only way to see deep down on the insulator.   Watch out for the specks of dark "fly sh**" which signal danger.    Small aluminum beads or balls are self-explanatory.    Inspect the side electrode for "spark mark".    It is the best indicator of "tolerable" advance.

Best advice is:   Find a spark plug tech from one of the manufacturers who will show you what to look for.    And keep in mind that street plugs look different from race plugs.

Also:  If you suspect it is hurt,  STOP and do a thorough evaluation, including a compression and leakdown check.    Slightly weak engines are always better than a broken one . . . . . .

Hope this helps.
 cheers
Fordboy
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Scottie J
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« Reply #94 on: February 12, 2015, 09:51:53 AM »

Thanks for the input.  And yes, the right cylinder is just slightly richer than the left.  I believe this is due to the left primary pipe being 4" longer than the right, and slightly better scavenging.


Does this pic help any?

« Last Edit: February 12, 2015, 09:55:43 AM by Scottie J » Logged
fordboy628
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« Reply #95 on: February 12, 2015, 10:04:20 AM »

Thanks for the input.  And yes, the right cylinder is just slightly richer than the left.  I believe this is due to the left primary pipe being 4" longer than the right, and slightly better scavenging.


Does this pic help any?



Yes, that's better, but get the plug magnifier anyway.    Looks like street plugs?   Notice the difference in side electrode appearance, due to the difference in mixture strength.   Everything affects everything else . . . . . .

Those little differences between cylinders add up.    And that's the trick, to get every cylinder equal AND optimized . . . .

Be happy you don't have a V12 . . . . . .
 cheers
Fordboy
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« Reply #96 on: February 12, 2015, 11:15:52 AM »

Yeah, buying plugs in quantities of 12 used to be no fun. I'd ask the counter man for some Champion xxx and he'd always bring out a pack of 8. He didn't want to sell 4 more loose plugs. Guys running 4 or 6 cyl engines probably had the same problem.

When I registered my car in AZ (a long time ago) the girl at DMV asked "How many cylinders?" I had to convince her that a car could actually have 12 cylinders.  grin

Regards, Neil  Tucson, AZ
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Regards, Neil  Tucson, AZ
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« Reply #97 on: February 13, 2015, 02:05:11 PM »

All good...............consider that leaded or unleaded high-octane race gas with a colder plug will be more difficult to read........especially if you start out somewhat close to optimal................I've also noted on my single and 4-cylinder bikes that 3rd-gear chops read differently than top-gear chops.  I've given some thought to doing a plug-chop at the end of my first run.............. 
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2011 AMA Record - 250cc M-PG TRIUMPH Tiger Cub - 82.5 mph
2013 AMA Record - 250cc MPS-PG TRIUMPH Tiger Cub - 88.7 mph
2016 AMA Record - 750cc M-CG HONDA CB750 sohc - 130.7 mph
2016 AMA Record - 750cc MPS-CG HONDA CB750 sohc - 137.7 mph
Chasis Builder / Tuner: Dave Murre
Scottie J
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« Reply #98 on: February 14, 2015, 09:18:18 AM »

I think my ignition coil has crapped on me.  It is the coil that came with my Thorspark EI conversion, it replaces the points plate in the mag with a trigger plate and external coil.  Bike has been running great, but Thursday I tried riding it home about 30 miles, and after about 20 minutes of riding, it developed a bad misfire.  So bad, I had to get off the highway and call a tow truck.  It's doing the exact same thing that stranded me last year before the tear down and rebuild.  At that time, I thought is was a bad fuse holder, and that I had fixed the problem with the new wire harness.  However, I haven't ridden the bike long enough until Thursday to recreate what had happened last fall.  I emailed the company where I got the ignition, and they said

Quote
Hi, the primary resistance should be around 4.5 to 5 ohms, we have used a few different batches of coils over the years, but all should be roughly that.

Primary resistance is testing 4.7ohms, but there is absolutely NO secondary resistance, no matter how I try to test it.  Oddly enough, the bike stills starts on the first kick without any throttle.  Yesterday after testing the coil, I rode around the block, replicating the exact same riding conditions that was causing the misfires the day before, and not 1 single misfire at all.  I'm currently looking at replacing the coil with a 3 ohm Dyna Coil DC6-1.  Any thoughts?

Here's a short video of the testing.
https://www.youtube.com/watch?v=OgFDQJ7zjdE&feature=youtu.be
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Queeziryder
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« Reply #99 on: February 14, 2015, 11:04:16 AM »

Scottie,
Very Important.

DO NOT use a 3 Ohm Dyna coil, you will over stress the Thorspark ignition. evil
Dyna will supply a suitable coil if you ask them.

DAMHIK
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Scottie J
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« Reply #100 on: February 15, 2015, 10:47:19 AM »

Scottie,
Very Important.

DO NOT use a 3 Ohm Dyna coil, you will over stress the Thorspark ignition. evil
Dyna will supply a suitable coil if you ask them.

DAMHIK

Yep.  Just that I spoke with Dynatek before I heard back from Thorspark, either way, that same Dyna coil comes in a 5ohm configuration as well.  Anyway, I spent the whole afternoon yesterday troubleshooting the ignition.  After replacing the HT leads and plug caps, no matter what I do I can't get secondary resistance reading from the coil.  I even ran some errands up to Lowes a few blocks away, and afterwards continued riding around my neighborhood.  Sure enough, after about 25 minutes she started to misfire again.  I just sent this email to Thorspark, so let's see if they actually do anything or not.  Regardless, I think I'm still going to buy a Dyna coil.


Quote
Hi Chris,

I normally don't waste my time writing letters of disappointment, and just cut my losses and call it good.  But I have to say that I am extremely disappointed with the quality of the coil provided with the Thorspark ignition conversion.  While the ignition does do it's job and is much better than the original points/mag set up, I just can't believe that an ignition coil cannot even make it 10,000 miles or even a full 2 years.  Twice now, I have been stranded on the side of the road and have had to call for a tow truck to come rescue me.  As of recent, the bike runs great for about 20 minutes and then develops such a bad misfire that it renders the bike un-ridable.  The first time it had happened was on last years Distinguished Gentleman's Ride.  Not only did I get stranded out in the middle of no-where with no phone reception, but it happened before I even made it to the second stop of the ride.  I assumed at that time it was the cheap fuse holder you provided for the ignition source.  I had replaced it with a blade style fuse holder, and thought that I had solved my problem.  But only going on 2 short rides to the store before tearing the bike down for a rebuild, I hadn't run the bike long enough for it to fault again.  A couple of weeks ago, I finished up my winter rebuild.  I shook the bike down for 2 weeks making sure I had the bugs worked out and decided to ride it home from my shop.  20 miles into the ride the bike starts misfiring as I'm doing 70mph down the highway in heavy rush-hour traffic.  Thank the good lord the bike had not completely stalled causing me to crash in the middle of traffic.  Once again, I had to have my bike towed back home.  I have now spent the last 3 days troubleshooting every single possibility in the ignition system and rest of the bike.  The battery is new and has a full charge, the wiring harness is a brand new custom built harness with soldered connections and bullet connectors only where needed, the kill switch is new, and the fuse panel is new.  The entire electrical system is BAND NEW.  However, no matter what I do, I CANNOT get a secondary resistance reading from the coil.  I even removed the HT leads, and replaced them, and even at the terminals on the coil, there is absolutely no secondary resistance at all.  After discussing my current issue with my engine guy, he too agrees that there is a fault with the ignition coil, and even made a remark along the lines of that "it must be the crappiest coil he has ever heard of to die within less of 2 years".

I don't want to give off the wrong impression and imply that I am bashing your product, as that is not my intentions and would also be unprofessional of me.  However, I do have a bit of buyers remorse, when I consider that I could have bought a full digital Power/Arc racing ignition for the same exact price that I payed for the Thorspark.  But one thing that sold me on the Thorspark is that you advertised it with a 5 year warranty.  I seriously have only put MAYBE 7500 miles on the bike since I built it with the Thorspark 2 years ago, and let's not fool ourselves, that just isn't acceptable.  I hope that this problem can be resolved in a timely professional manner.  I have liked the product up until now and hope that I do not need to replace it after only a very short times use.  Thank you for your time and I look forward to your response.

Scottie Usher

Bulldog Kustoms Denver
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« Reply #101 on: February 16, 2015, 11:31:17 AM »

Scottie;

It is possible to have a spark from a coil but still measure an open circuit in the secondary winding. What happens is that the secondary winding develops a small open circuit-- possibly due to a break in the wire or a connection to a terminal-- that an ohmmeter reads as an open circuit but the break gap is small enough that the high voltage spark will jump across.

This puts an additional spark gap in series with the gap of the spark plug- not good for a reliable ignition.

Regards, Neil  Tucson, AZ
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Regards, Neil  Tucson, AZ
Scottie J
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« Reply #102 on: February 16, 2015, 05:22:36 PM »

I sent an email to the manufacturer and explained the scenario and they agreed that the coil has failed.  They are sending a replacement under warranty, but probably will take a week or so to arrive from the UK.
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Scottie J
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« Reply #103 on: March 09, 2015, 07:42:37 AM »

Not much going on around here.  I received my replacement coil last week and got that installed.  Tests were indicating it is good for 40,000 volts, so plenty strong.  The few short rides I've been on I haven't had any misfires, so I hope that problem is gone.  Tho, when I topped off with 92 octane yesterday she started detonating again when I'd pull over half throttle, I still have a gallon of E85 at work so I guess I'll have to put that in there again.  Thinking I may need to retard the ignition another degree or two as well.

Anyway, I wanted to bring up a topic that was discussed (either on this build thread or my old one) a while back, but didn't get a lot of attention.  It was the idea of reversing the fork legs around backwards to increase the rake and trail.  Recently while going thru some old threads on the BritBike forum, I found discussion of a couple of guys doing this to their old Ascot racers.  Tho there was a bit of debate of whether this actually works outside of flat track racing.  Legend has it that flipping the fork legs around does in fact increase the rake and trail and sharpens the cornering, and may have helped lead Guy Lewis and Elliot Schultz to being so successful at Ascot.  So while, it sounds like this would be an advantage for flat track and road races, my concern is how well the bike will track on the salt.  So far, I have only gotten the bike up to 95mph on pavement (due to never being 100% happy with the tune and constantly playing and discovering 50 year old problems), where it just starts to develop a bit of a speed wobble.  I have noticed that the lower the air pressure in the tires the lower the speed the wobble starts.  I have also been looking into cartridge emulators for the forks.  There are a couple of people on the Enfield forum that have done this mod now and are really liking the improvement in handling for about $100.
 
Any expertise in this department would be greatly appreciated.  Thanks!



Here is the Shell Thuet tuned Bullet that was very successfully raced at Ascot by Guy Lewis and Elliot Schultz.
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« Reply #104 on: March 10, 2015, 10:40:23 AM »

Scottie,
Reversing your forks will of course move your front wheel back maybe 2 or 3" which will definitely increase your trail by that same amount.  It moves the center of the wheel back from the steering axis (a  line drawn down thru your head stock center bolt) which lengthens the steering arm and makes turning in either direction require more force.  It does not increase rake.  It actually slows down the steering.  This is considered a good thing in land speed racing, but it doesn't prevent speed wobbles by itself.

In my opinion, speed wobbles can be caused by any of a number of undesirable characteristics of your steering, wheels, frame, etc.  A few things that you should look at are wheel balance, wheel run-out, wheel straightness, wheel bearings, spoke tightness, tire pressure, forks bushings, fork oil and springs, triple clamps bolts, axle bolts and axle caps, center bolt bearings, center bolt tightness (not too tight but no play), frame stiffness, swing arm bushings, swing arm stiffness, as well as rear wheel issues as above.   Any or all of these things can contribute to initiating a speed wobble and the old British forks are not strong enough to allow the steering to recover if it does get into a wobble. A good steering damper strongly mounted can help but will not solve all the issues.  In short, every part of the bike is important and becomes more so as speed increases.

Tom
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