Chinese Clone Motor on Gas‏ – Engine Dyno

Here’s a dyno pull comparasion of a Chinese yellow clone motor on gas. We started with a stock engine with a stock muffler, put in 16 oz. of 10w30 oil and did a couple of dyno pulls. Engine ran very bad, sounded like a bad spark plug. As you can see by the lower dyno pull engine surged very bad due to very lean condition. Made 4.6 hp at maximum at 3000 rpm. First thing we did was remove stock muffler and replace it with a small header we got from ARC.  Really didn’t help much, engine still very lean. Drilled main jet out to .037″ and dyno again. Engine souded very strong and made big jump in horepower. We then tryed Animal springs instead of stock springs. Really didn’t do anything, in fact lost hp on top end. Went back to stock springs and stuck on large RLV header. Made a pretty good jump in hp. Ended up with large RLV header and .036″ jet. I don’t think this header will be legal for the rules that I skimmed thru very quickly but just for your infomation. I think the small header from ARC ran best with a .035″ jet.  I know A.R.C.  & J.C. Specialtys both have parts for these.
About 5400, this motor really fill off. A couple of people have told me spring pressures will make a big difference but they will not be legal!
The dyno sheet show a comparision of a bone stock engine with how we ended up with all stock parts except for jet change. Tightening valve lash settings didn’t make much differance. Ended up gogin back to .003″.  Max torque was at 3600 rpm, peak hp at 4900 after jet change.

Interested in Purchasing a Hewitt Inertia Dyno?

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Stan Hewitt
c 641-512-3395
hewittdyno@gmail.com
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CLUTCH DYNO TESTING on a Hewitt Inertia Dyno

CLUTCH DYNO TESTING

A lot of you ask about dynoing a clutch. It’s very easy! Open your software to the dyno screen, put in your correct ratio, sprocket number divided by clutch driver size. In this case, 53 tooth divided by 16 tooth clutch driver, =3.31. Start your motor up; hit the gas to wide open throttle. Do this a minimum of at least twice to warm up clutch. Watch the flywheel rpm screen to see about what engine rpm the clutch is slipping at currently. After a few seconds, the rpm will go higher (clutch locks up or quits slipping). I always recommend you take engine rpm to a minimum of 5500. Down load data and look at it. Graph it with using clutch /converter slip in relation to engine rpm. On this print out, you’ll see clutch engages at 3100, slips up to 4 to 1 ratio which isn’t real bad, then has total lock-up at about 4050 rpm, were line is almost flat again. This example is a JRII IKF motor with a .500” tapered restrictor. You’ll learn after a while that the clutches with sintered metallic discs tend to be the best. The ceramic and organic discs do not seem as good. On the real low hp engines, some people like the clutch to slip a little so it does not bog the motor. This depends on your preference of what works for you? Motors with higher horsepower tend to slip more! Lower numeric gear ratios tend to slip more!

How to do the test? On the second rpm pull to warm up the clutch, brake flywheel rpm down to 900 rpm, engage data system, wait a couple of seconds, go wide open throttle, take engine rpm to at least 5000. Download & look at data by graphing it. Remember with Pro software you can look at data in time/seconds just to see how long it took clutch to hook up. Remember you can also do up to six overlays in graphing mode.

If you have a customer getting killed on the starts or restarts and then he/she runs them down and passes people later in the race, they may have a clutch problem?

Also if you race at a track the uses Calcium Chloride, you’re much more apt to have sticking levers on the clutches. No chemicals seem to remove the oxidations. The only way I found to get clutch back to normal is take it apart and file out area were levers actually work. Then maybe spray a clear acrylic over the area to keep it from happening again?

High Horsepower Dyno – Hewitt Inertia Dyno

This is a dyno for someone who wants to dyno engines from 4 hp up to 100 or more. It uses just a simple mechanical coupler to add one or more of the flywheels. I have four of these dynos in the U.S. We normally install a larger axle to eliminate axle flex of the higher horsepower engines. This machine also had a electrically controlled hydraulic system which could be controlled out side of the dyno room to heat the engine head temp up to 300 degrees or more.  All data systems come with a S.A.E. weather correction system. Most customers order head temperature and some use a exhaust sensor in the crankcase oil to make sure engine is up to temp. Air/fuel ratio is now available as an option.  Questions?  Want to purchase? Call me…

Sling Shot Inertia Dyno – Hewitt Inertia Dyno’s

Used on v-twin briggs engines on dirt type race cars. We made a quick change #40 chain two piece split sprocket so he can change from 3-to-1 or 4-to-1 ratio. This engine has electric start so he just hooks up battery, starts engine, turns on the data system and hits the gas. This dyno is accurate to 1/10th of a horsepower & also is a clutch dyno. Measures engagement rpm, slippage ratio and also measures where total lock-up of clutch occurs.  Interested in a Sling Shot?   Give me a ring.  Stan