Combat Wombat max HP or torque

[DGardner]

2000 rpm is when the dyno run started that's why it goes straight up there.

[Bullfrog]

I was having real trouble swallowing the dyno run . . . was real skeptical about the comments about a single hole piston for reed porting . . .

. . . then comes the piston with holes (photoshopped?) surrounding the ends of the wrist pin and a really odd (dry rust covered? OK, wood as it turns out.) . . . and I had just about reached the end of the rope. Still, I decided I'd ask one round of questions to confirm the main thought running around in my mind. And that main thought was something along the lines of, "This is such a pile of bull****!"

I'm really bummed that we may not get the dissertation explaining just how those holes surrounding the wrist pin work. That's got to be a true creative work of the wordsmithing arts!

Ed

[Zyx]

Probably a proprietary process of RK Tek.

[DGardner]

Okay.....I thought that the two piston photos was funny and that everyone could tell that it was a joke. The dyno runs are real and the piston like I first said (not the one with the holes in the side that was a joke) started out as a new combat wombat piston from Paul. The first run was made with the combat wombat piston the way it came from paul the second run is with a hole in the center of the piston about 5/8 inch wide and I would say 3/4 inch long and starts about 1/2 inch above the bottom of the piston. Again the photos of the pistons was me trying to be funny sorry if it didn't come out that way.the second dyno is real also it's a 1900cc bike and the test started at 2000 rpm and ended at 5500 rpm. The wombat run started at 3500 rpm and ended at 7500 rpm. Again sorry if the piston photos was not seen as a joke.......by the way the wooden piston I hear came from a bike in Vietnam. DG

[swcaudill]

Piston looks like it is wooden. Oak for high performance or maybe pine to soften the power.

[MWL]

Good one Doug!

[hodakamax]

I got it, and thought it was funny! The multi-hole one would not have much of a service life.

Maxie

[DGardner]

This is some of the photos of Roger having his wombat put through the test on the dyno yesterday.

[DGardner]

Make your guess on hp and tq at what rpm for a stock model 94 with the only mod being 10 thousandths off the head. I think Roger is going to post the dyno later today.

[Dale]

Sufficient?

[Zyx]

12 give or take. Enough to get down the road.

[dcooke007]

Hey Doug,
I appreciate the info you are gathering and having base line info for stock Hodaka models would be handy. To me having this info would be helpful in evaluating engine modifications for performance increases. I appreciate any info you share here.

I know the wooden piston and holes in the piston joke might not have gone over well but hopefully every one can over look that.

Danny

[rlkarren]

I was following this post with moderate interest because some of the technical details werea little beyond me... however when Doug mentioned taking my Australian Marsupial down to run on the Dyno I really jumped on the chance.

A couple disclaimers...

1. The bike has never run better than now. Perfect timing to test it and see where it sits on performance. The bike is completely stock except the head was slightly not flat so I had between .008 " - .010" taken off the head and cylinder deck combined, (according to the machinist). Bored .010 over with about 3500 miles on the piston. I've changed bearings and seals a couple times since full rebuild.

2. We couldn't get a steady inductive signal from the timing, (I have analog ignition, where Doug has electronic on his), so we had to calculate RPM's via the rear wheel gear ratios. It's not exact but it's very close.

So while I am very happy with it's performance. Ed was right...

Several of us could give you a pretty good ball park number without the advertising agency inflation factor, but you'd probably be disappointed.

First run was with a 135 main jet, and indicated I was burning rich. Dropped to a 130 Main and got improved results although still a little rich.

Now, if I read the chart correctly, Max HP was 8.85hp at 5870 RPM's, max torque was about 8.00 lb/ft at 5700 RPM's.

Now don't get me wrong, the bike performs great! It's very responsive and gets up and goes with lots of pull when you get on it... But the numbers show, it's a great Trail Rider with lots of room for improvement. And possibly also shows why Hodaka stopped publishing numbers compared to the inflated numbers coming from the "Big 3".

$0.02

Roger

[DGardner]

This is a overview of the two dyno runs and as you can see Rogers bike is slightly rich and my bike was way lean on the bottom and at about 5000 rpm and that could be causing the flat spot at around 5000 rpm. I've been working on that and hope I've got it closer now. One thing I would like to try is take out the reeds that I got from Rich and put a stock pair in with a stock 03 intake with the reed stuffer to see if it would give more bottom end over the reed that was opened up by Rich.

[Zyx]

Two things, first I would have to know how fuel/air is being tracked before I believed anything about it other than general trends; two, I think the power output on the 94 is too low, and might be farther off than you think by using gear ratios to compute engine speed. Using gears to determine rpm also requires careful calculation of actual running diameter of the drive wheel, allowing for slippage. Too many variables to be accurate, although as long as the results are repeatable, you can use them to track changes.

But assuming you ran two different Hodaka 125's in the same week or so, either the first bike read way high, or the second was way low. They are different in their output to be sure, but not that different. Our old 100's made 8 or better. I would revisit the rpm calculation on the second bike.

[DGardner]

The hp is correct it would only be the tq that would be off on the stock bike......but if you look at the specs that hodaka published peak tq was at the same rpm. So I would say it is close.

[rlkarren]

Yeah, I know. It's pretty hard to accept when the computer spits out numbers we don't like.

What you see is only two of many tests we ran. Since we couldn't get a steady spark from the analog ignition, the first tests didn't even use RPM as a base line and tested Horsepower alone. If memory serves, the first test registered 8hp. That's when we started laughing that not only was it "disappointing, but 'shockingly' disappointing". Then I changed jets and it came up to about 8.5 hp. Each test consistently came up with roughly the same number. We posted the best results.

Then... in order to try to get the torque reading, we needed to use RPM's so we put Doug's bike back on. We have the same gearing for 4th gear so we determined the gear ratio input using Doug's bike. This was done by first running an RPM test, then running subsequent tests to get close to the same result from that day and all the tests before, using gear ratio input. After achieving what we felt was the correct input, my bike goes back on. Ran the same test using the determined gear ratio, and voila!; it spits out the same numbers for HP and a very believable torque. We know it's not exact and maybe marginally scientific, but we do believe it's very close.

As for the argument that there are too many variables when using gear ratios to determine RPM's, I think the computer took all that into account. While it may be a formidable task for us to manually compute RPM's using gear ratios, it's a trivial task for even a modest computer.

Fuel/air was measured with a Oxygen sensor in the exhaust pipe. Again, based on performance before, during, and after, I would say it was dead on. We had a 40 minute ride each way and the bike certainly performed better on the way home with no hint of overheating on a very smoky 80+ degree day.

As much as we might not like it, a stock Wombat is probably 9hp @ 5900 RPM's at it's best. And if torque is consistent with other Hodaka specs, peak torque is achieve at roughly the same RPM which is about 8 - 8.5 lb/ft.

If someone wanted to send me a PowerDynamo kit, I'd be happy to run the tests again. I'd be willing to bet the tests will be roughly the same. Maybe a little improvement with a better ignition though.

I have to mention too, that the charts show a real world difference in performance between mine and Doug's Wombat. The differences you see on the chart manifest themselves on the road as well. In an attempt to illustrate: Doug is very high geared, using a 16/47 sprocket combination. I'm using 15/54. Even with his high gearing, Doug can easily leave me sucking dust at 50 mph. Where I'm at 7/8 throttle in 5th gear, Doug is maybe half throttle @ 50mph. Even at that speed, when he gets on it, he pulls away easily and quickly. Where my stock bike struggles to achieve 55 mph with a 15/54 combination, Doug pulls 65+ mph using much higher sprocket gearing. So in my own observations, the charts match what I see on the road when we ride.

Being skeptical is OK, and I am naturally skeptic or maybe cynical would be more accurate.. but I am satisfied our tests are accurate, at least much as is possible. I think the only thing that would convince me otherwise is another stock Wombat with very different results.

Roger

[Zyx]

If you're happy, I'm happy. It isn't my bike. But as for computers making life easy, perhaps you have heard the adage garbage in, garbage out. Computers crunch numbers well, but can't differentiate between fact and fiction. Your tests are based on a number of assumptions, not the least of which is two bikes with the same fourth gear must run at the same rpm in fourth gear. That's an assumption. It may be right, but it is only an assumption.

Basing quantitative science on assumptions is nuts. I don't buy the 8 hp unless your bike is unusually anaemic. Which it may be. Since you don't have a real baseline, there is no way to know. If you had two or three stock 94's to test, you might start drawing conclusions.

I also don't accept a tailpipe sniffer as being anything like accurate in determining fuel/air on a two stroke bike. They are only broadly accurate on four strokes. It will show trends if it has any degree of precision, but as for accuracy, unless you have a verified standard for comparison, it tells you little you can use. I surely would not tune based on the readout from a sniffer. Just because it ran better after leaning is not an indication of accuracy. Any bike will run better when lean until it goes ragged on you. So right now, you don't know if your jetting is right or it isn't, and without further experimentation, you don't know if your pipe is clogged, if your air filter is defective, if your gas is too old to use, if your compression ratio is too high for the gas you use, if your oil ratio is too rich, if your plug is too cold, or any other variable that went unaccounted for.

The combat wombat in stock trim was limp. But as I recall, the combat in this case is running an 03 cylinder and reeds, which is very different from a combat wombat running piston portion take, and worlds different from a stock 94.

True science requires removing variables until you are testing only one at a time. Not easy to do with a rear wheel dyno. In this case we don't even have a means of filtering out parasitic losses, and we don't know if this dyno is calibrated for ten horse vintage motor bikes or 100 hp blacktop burners. So, interesting I suppose, but I wouldn't rely much on the results as other than an interesting thing to do.

Here's what you can do with a dyno in a case like yours: use your last runs as a baseline. Numbers don't matter. Then change something like an air filter, an exhaust system, a piston style, or reeds versus piston port, heavy weight trans oil versus ATF, something like that. Compare results. You can tweak your way into more performance this way, but the numbers you get are relatively useful, not correct. Correct is a conclusion, and we don't have enough data here to make such a conclusion.

[hodakamax]

Of course in the old days manufactures measured HP off the crank and rounded it up to the next higher number and other ways of fudging. Rear wheel readings add drive train drag to the results. To a 100 HP bike the drag of the drive train, let's say, is 5 HP or 5%. Real driveline drag is probably almost the same on a 15 HP bike making it 10 HP at the rear wheel or 33%+ loss. The dyno is probably not lying, the 100 HP bike is only losing 1/20th of its power whereas the 15HP bike is losing 1/3 of its power to driveline drag. Food for thought.

Maxie

[DGardner]

I think your correct Max! Even Arizona said the factory rated off the crank and that it was inflated with the ace100 being 9.8hp and 6.7 tq....100B 10.5 and also 6.7 I don't think 9hp at the rear wheel is out of the question. It would be a lot better if we had 100% correct rpm.....but for now this is as close as we can get. DG

[dcooke007]

Maybe the dyno testing is not as scientific as possible but it is the only dyno info I have ever seen for a Hodaka. Something to think about.

Danny

[Kels]

Dynos are a tool and can be made to produce any number you want it to.

Having said that, this dyno is 100% neutral and the owner is honest.

There would be no reason to falsify any data.

Doug's engine show about a 60% increase in HP output over Roger's and as stated by Roger, this added HP manifests itself easily in the real world..

Like Danny stated, not many dyno reports on this engine modded or stock.. If you have one from a neutral facility, then please share it..

Discrediting any dyno report without data to substantiate the dis-creditation Or simply because you do not like the results..... is simply unfair.

[hodakamax]

Dynos are a tool and can be made to produce any number you want it to.

Having said that, this dyno is 100% neutral and the owner is honest.

There would be no reason to falsify any data.

Doug's engine show about a 60% increase in HP output over Roger's and as stated by Roger, this added HP manifests itself easily in the real world..

Like Danny stated, not many dyno reports on this engine modded or stock.. If you have one from a neutral facility, then please share it..

Discrediting any dyno report without data to substantiate it..... is simply unfair.

"Unfair" is the word. The Guys seem to be doing a good job with the tools they have and are giving us real numbers for us to contemplate. I'm liking their experiments and they seem to make sense.

Max

[Bullfrog]

I have to admit that I would have predicted your Dyno report to show about 1 HP more than it does . . . and I would have expected the HP peak to be a bit higher in the rpm range than shown. It just seems to me that when I ride a stock Wombat (Model 94A) hard in the dirt, that it is useful to rev it higher than the graph would suggest (so I'm wondering a bit about the calculated engine speed too noting that my "butt tach" is not all that precise ) Still, the general shape of the graph seems right (no "hit" at some magic RPM and relatively gentle "fall off" after the power peak) . . . and the peak hp is within 10 - 12% if what I expected . . . so no real surprises there.

NOTE: We KNOW that the snorkel of the air cleaner cover is restrictive. The opening is too small and the rubber comes toooooooo close to the element on the inside creating a second "pinch point" for air flow into the air cleaner area. Simply removing the snorkel AND going up a size on main jet for engine safety would improve the graph. (Existing condition is that the main jet is sized to match the inability of the air cleaner system to deliver copious quantities of air.) But make those modifications and you are no longer talking about a "stock" Wombat.

Ed

[Bullfrog]

PS: I'd still like to see a photo or diagram of the single hole piston used in the reeded bike.

Ed