Author Topic: Honda CX500 - EFI and boosted on a budget M-PBF 500  (Read 9913 times)

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Offline lucasanderson00

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Honda CX500 - EFI and boosted on a budget M-PBF 500
« on: February 24, 2018, 01:39:48 AM »
Here is our CX build already in progress, more of an evolution than a build at this point but here it is anyway! It started as a lofty goal between myself (Luke) and long time friend Sean. We started out with a bone stock '79 CX500 that was traded for broken down '61 Rambler plus 600 bucks on their end. Great start, and it made up for its looks with how well it ran. We took it apart right away.

The first picture is in 2014, the bike already had its big 23" tire, chosen to get some more mph since the final drive gearing was fixed being a shaft drive and all. We also swapped a CX650 transmission and clutch/primary for even more gear. The BW K03 turbo was mocked up and I was stoked.

It took a couple years in our spare time to get the bike running again, fabricating the intake, exhaust and fuel tank. All the finish TIG welding was done by my friend Jerry Westhouse (and all the ugly MIG welds done by myself). We installed a Honda CBR954 front end and a Megasquirt II EFI system, initially controlling fuel only.

The second picture is at the Ohio Mile April 2016. We went to 2 OM events that year and set 2 records, 1 in an open class. Best speed of 123.8mph. We had clutch slip issues and ignition problems with our stock coils. Datalogging was also not working and we had no data to go off of, EFI had a steep learning curve to say the least.
« Last Edit: February 24, 2018, 01:42:04 AM by lucasanderson00 »

Offline lucasanderson00

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #1 on: February 24, 2018, 02:20:30 AM »
After the 2016 season we fine tuned the bike, a lot was learned at Ohio Mile.
Post season changes:
-Charging system
-Coil near plug ignition
-AEM cam sensor driven off the old mechanical fan snout
-Barnett clutch
-Airtech seat cowl...that stock seat was so ugly and way too high up
-3D printed carbon composite turbo inlet elbow
-1600cc injectors for M1 methanol
-datalogging sorted out

The next goal of course was Bonneville

Offline thefrenchowl

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #2 on: February 24, 2018, 04:37:31 AM »
Hi, Luke

That big rear wheel gives it an angry stance!!!

 :-o

Like it...

No intercooler plans?

Patrick
Flat Head Forever

...What exactly are we trying to do here?...

Offline lucasanderson00

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #3 on: February 24, 2018, 11:51:05 AM »
Yep that wheel certainly gives it a unique look! No intercooler plans on this one...unless it becomes absolutely necessary.

Offline lucasanderson00

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #4 on: February 24, 2018, 12:11:26 PM »
Spring of 2017 - we built a second engine with higher compression intended for methanol.
CP made the pistons, they have a 22 degree twist due to the head design on these engines. 11.5:1 compression
Flatout gaskets supplied us with custom headgaskets.
We now had 2 different setups-
Engine 1 - 10:1 compression with 550cc injectors for the gasoline class
Engine 2 - 11.5:1 compression with 1600cc injectors running alcohol in the fuel class

Offline Koncretekid

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #5 on: February 24, 2018, 05:08:10 PM »
I'll be following your progress.  Fuel injection plus supercharging - - food for thought for my BSA.

Tom
We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!

Offline lucasanderson00

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #6 on: February 25, 2018, 12:14:18 AM »
We made it to Bonneville Speed Week in August 2017, very exciting, first time out on the salt. We roughed it in a tent at the KOA. Tech went well, no issues. Both Sean and I made our rookie runs and got our licenses, running in the 110-120 range. That course was very rough and was an eye opener to say the least. We moved over to the short course and I made several passes over the next couple days tuning and making an attempt at the M-PBF 500 record of 126.9mph. Monday the bike qualified and went to impound. Tuesday morning we experienced acute rod failure on the record attempt after I over-revved the engine at the top of 4th gear(oops). One rod cleanly separated itself at 10,500rpm and swung through the transmission (located in the crankcase). The countershaft sheared clean in half. We went back to the pits and swapped in the low compression engine and got back in line. We made the last pass of the day with Sean riding and requalified. The next day the bike ran 141mph and set the new record at 133.1mph. Good times!

Offline thefrenchowl

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #7 on: February 25, 2018, 06:41:27 AM »
Quote
One rod cleanly separated itself at 10,500rpm and swung through the transmission (located in the crankcase).

Jeeees, this must have made the most horrific noise...  :-(

But you got a record 1st time out, so good preparation no doubts...

Felicitations...

Patrick
Flat Head Forever

...What exactly are we trying to do here?...

Offline fordboy628

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #8 on: February 25, 2018, 08:34:43 PM »

We made it to Bonneville Speed Week in August 2017, very exciting, first time out on the salt. We roughed it in a tent at the KOA. Tech went well, no issues. Both Sean and I made our rookie runs and got our licenses, running in the 110-120 range. That course was very rough and was an eye opener to say the least. We moved over to the short course and I made several passes over the next couple days tuning and making an attempt at the M-PBF 500 record of 126.9mph. Monday the bike qualified and went to impound. Tuesday morning we experienced acute rod failure on the record attempt after I over-revved the engine at the top of 4th gear(oops). One rod cleanly separated itself at 10,500rpm and swung through the transmission (located in the crankcase). The countershaft sheared clean in half. We went back to the pits and swapped in the low compression engine and got back in line. We made the last pass of the day with Sean riding and requalified. The next day the bike ran 141mph and set the new record at 133.1mph. Good times!


Unloaded "over-rev" connecting rod tension loads @ TDC overlap can be fearsome.   Use one of the engine analysis programs to calculate the load in G's.   The piston in the photo looks like it might be a bit on the heavy side, but it is hard to say for sure.   You are going to need very light, premium quality parts for reliability at high revs.

 :cheers:
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Offline JimL

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #9 on: February 25, 2018, 09:55:16 PM »
First off:  Good job!

I ran these CP pistons for years in my CX engines.  I often took them beyond 11,000 and never had a problem.  Take a good look at the wrist pin bores and the pins themselves.  I changed pins a number of times because they did not seem to oil well.  CP and I had a few brainstorming sessions about pin lube issues (on other engines as well).  I started putting the pins in with Lucas zinc-additive oil to buy a little more time.  I think it helped, but your mileage may vary.  I always wished for a row of parallel ridges across the bottom of the dome, but never got it (oil droppers for the top of the rod).

That said, look very carefully at the rod installation.  The oil hole orientation is easy to get wrong and that will reduce oiling into the wrist pin on an affected cylinder.  They run fine with a rod in backwards....until something goes wrong.  It is very easy to get these in wrong because the only rod big end access is through a pair of (rough, nasty) holes that are knocked through the inner crankcase during manufacture (absolutely bizarre manufacturing process).  As you already know, installation is done by feel through a sharp-edged hole and often includes some well-oiled blood (your own) inside the cases.

Pretty fast motors, all things considered, but really expensive to build heads that breath well.  If you are really careful, you can cut the 500 valve seats to take CX650 valves.  I had better luck with aftermarket valves and going down to 5.5mm stems (with appropriate bronze guides).  I also ran shorter springs with about .25" tall isolators under them to let the oil flow reduce the rate of exhaust heat getting into the bottom of the exhaust springs.  You may find your springs get too hot (and soft) at the end of a long pull.  The ports are too low and too sharp and so the top of the exhaust port gets smoked pretty quick.  

Watch for "pop out" pitting on the back slope of the cam lobes....that will tell you for sure if the exhaust valves are starting to float.  Those pits may be pretty small, but if you find them....you are in trouble.  The cams keep working fine, even after they pit, as long as you solve the float problem.

Like the previous post says, over-rev is ugly and uglier if you chop the throttle instead of powering into an upshift, or a brake, to pull the revs back.  With the throttle shut at high rpm, there is not enough intake air for the compression to help slow down those pistons.  I was taught to push into the rear brake (throttle still open) to capture an over-rev.  Easy to do on a bike.

JimL

PS....almost forgot to mention.  The shim stack behind the last gears on the shafts is a little tricky and can lead to missed shifts.  We also had a shaft slide in the clutch side shaft bearing, which makes the bike want to stay in 4th gear.  Just food for thought.  If you are ever putting one of these engines (with the home-brew trans work) together....and one day you pull the clutch lever and hear a little pop (and suddenly have a little extra slack in the cable) your shim stack is wrong and the input shaft has slipped in the clutch side of case bearing.
« Last Edit: February 25, 2018, 10:05:25 PM by JimL »

Offline Koncretekid

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #10 on: February 26, 2018, 07:49:53 AM »


Unloaded "over-rev" connecting rod tension loads @ TDC overlap can be fearsome.   Use one of the engine analysis programs to calculate the load in G's.   The piston in the photo looks like it might be a bit on the heavy side, but it is hard to say for sure.   You are going to need very light, premium quality parts for reliability at high revs.

 :cheers:

Looks like the rod is the culprit, not the piston.  Can you get Carrillo or equal rods?

Tom
We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!

Offline lucasanderson00

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #11 on: February 26, 2018, 10:32:37 PM »
Thanks guys!

Jim, so much good information in just 1 post!. I have been following your builds and you have been an inspiration to us for years. The CP piston is slightly heavier than the stock piece, which I knew putting the engine together but ignored. This year the plan is to have CP/Carrillo make us rods as well. Lucky for me, they are located half a block from where I work now that I moved from Chicago to Southern California.

I am interested in spinning this engine to 11k if possible though, so I'm glad to hear you have done it with success. My options are becoming very limited to get this bike over 150 with its fixed final drive ratio. Now it looks like they eliminated the shaved v-rated tire exception for speeds over 150 for 2018. I'll have to go back to a smaller diameter z rated tire.
The best solutions I have so far are possibly retrofitting a CX650 Turbo clutch, primary, and front cover onto our 500 engine(very expensive/rare and maybe not even possible but has a much better ratio), or getting custom primary or transmission gears cut(probably equally expensive)

Offline wobblywalrus

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #12 on: February 26, 2018, 11:34:10 PM »
Has anyone looked seriously at Honda's new 500 twin?  It looks like a good platform for an LSR build.

Offline edinlr

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #13 on: February 26, 2018, 11:44:36 PM »
Wobbly, the new 500 is nice, but since it is OHC, it runs with the big boys in G, good try trying to get all of us CX guys out of the pushrod classes.

That is interesting that they took away the shaved V rated tire rule, can anyone shed light on this, was there a problem?  There are a lot of the smaller bikes that run narrow tires and the selections are very limited when you get narrower than a 160.
Honda CX650 turbo, Kawasaki H2 Ninja, Kawasaki ZX750 turbo

Offline JimL

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Re: Honda CX500 - EFI and boosted on a budget M-PBF 500
« Reply #14 on: February 27, 2018, 12:21:27 AM »
This may seem counterintuitive....but:  if you want to spin fast you must cut the flywheel weight a LOT.  At high revs, the energy carried in a heavy flywheel adds to the stretch (and or) compression effect on the rod.  The rod is trying to hold opposing forces together.

Lighten the flywheel and save the rods (and a lot of other things).  If you don't believe it, look at the mini-flywheel used in modern F1 or Indy type engines.  Those folks know what they are doing.

Picture every part in the engine held together by rubber bands which always try to snap things back into place.  Big, heavy moving components don't like that kind of trouble.  Cut your flywheel down to just enough to hold the starter clutch.  And do not run an alternator.  It's just one more batch of pulsing forces tossed into the mix.  Two batteries is simpler and less stress on the engine.