Racing Improves Your Riding & Your Bike Beginners Guide to Socal Motor Bicycle Racing


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Jul 3, 2008
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Introduction to Motorbicycle Racing: A Brief Beginners Guide
by #108 Sander Sindell

Congratulations on making the decision to be a part of the countries lowest budget racing series, Socal Motor Bicycle Racing aka SMBR.

Herein you will find some crucial tips to keep you on the track, because by far the greatest challenge for beginner racers isn't being fast enough, it's finishing the race.

The beauty of SMBR is how accessible it is, with a decent bicycle and a $150 engine kit you could find yourself competing against other people with passion for the same hobby as you. But that doesn't mean you can just grab your beater and make a B-line to the track, well, yes you can, but there are some things you would be wise to consider before you pack up, gas up, and head out.

The beginner class is designed for low-budget racing for new and intermeditate riders using the China Doll predominantly, but also the 49cc Hausheng, friction drive or any other slower bikes. If you have high performance parts and a big expansion chamber and are way out in front you will probably be bumped up a class, however there aren't many rules per se; any class adjustments made are done to keep it fair.

At SMBR you will be pushing your bike to the limits, lap after lap, after lap, after lap, after lap, after lap, after lap, after lap, after lap, after lap... literally. That's 10 laps of racing in which you will be exerting a generous amount of stress on your motor and your bike, through high rpms, elevated engine temperatures, constant on and off full throttle torque to the rear wheel, constant tension and release of the drive chain, and above average loads on the bike in the corners. And that is just the Final race. There's also 2 six lap Heats that precede your Final in which you will be getting a taste of your competition and taking note of any last minute adjustments to make, which means, in total, your looking at about 17.6 miles of racing if your at the Grange, and whether your at the Grange or at Willow Springs, you will be in the desert, where it gets hot. Average temperature falls in the 80's but can reach into the 90's on occasion. My little china doll was running a crisp 360 degrees at the track in May, about 50 degrees hotter than I've previously recorded. She ended up doing well though and took 1st place in the beginner class. With that said let's move on to what you can do to increase your odds of finishing

First off let's take a look at what you can do to help keep your engine cool and prevent overheating. Side effects of overheating include pre-ignition and detonation of which syptoms can appear as pits in the piston and head, or even a blown a hole in the piston crown. Go and get yourself an infrared thermometer(they're cheap) and aim it right above the exhaust port to find out your operating temps.

- Tuning, Tuning, TUNING!!!!!! It is unbelievably important to tune your carburetor properly. It doesn't matter how many fancy parts you add, if your engine is running lean then it will run HOT. It might run alright for your normal city riding, but that won't fly at the track. Thankfully most of these engines run extra rich right out of the box, and might run alright or even good, but inevitably, since you are a racer, and racers modify stuff, you will end up rejetting your carb. When you do that, please, do not jet it too lean

You want to find the point where it's ever so slightly running rich and "4-stroking" and then jet it down one more size. I've jetted mine so anytime I'm at partial throttle it "4 stokes" lightly but as soon as I crack the throttle open she screams. Remember, the tracks that we race at are probably at different elevations from where you ride normally, which means your engine might run different at the track and may need to be retuned. This is one reason it's very important to come to the practice day before the race or at least early on race day, to dial in the jetting on your carb. So don't forget to bring different sized jets when your packing.

- Aftermarket billet aluminum head. This is my 1st upgrade for any engine because it adds power across the entire powerband by increasing compression AND it improves cooling. A win-win. You can typically see your engine run 20 degrees cooler with one, even much cooler than that in some cases. I use a Fred head from on my racing bike. Applying this upgrade will increase power and reduce heat, and you can still race in the beginner class with this modification.

-Spark plug heat rating. If you haven't already, ditch that crappy spark plug that came with the engine and get an NGK B8HS. The number 8 is the heat rating. For NGK plugs the higher the number the colder the plug. The stock heat rating is a 7 so a 6 is hotter(good for really cold climates) and 8 is colder(good for hotter climates and racing). Depending on your engines modifications and temperatures you might find that a different heat rating actually runs better(like a 7). Spark plugs are cheap so buy a few and find what works for you. It is not uncommon for spark plugs to be defective right out of the box, even NGK, so make sure your plug is good. You can Ohm test your plug with a volt meter.

-2stroke Oil. Pick a good one, I don't recommend running gas station oil. These engines have good enough gas mileage that it won't break the bank to run top shelf synthetic oil. More friction = more heat. Especially if your running your engine at high rpms. For normal riding at home your probably running 32:1, but on the track you want to run a ratio in the 20's, anywhere from 20:1 to 28:1. I'm not telling what oil I use so find out for yourself what the fast guys use and use that. Hmmmm, that is such a good tip that it deserves it's own line in capitals!!!!


You will find out things in a 10 minute conversation with someone that you would never have found out by reading stuff online. Pick up the phone, be friendly, and you might find yourself an insider to help you achieve better results <---Priceless.

-Fuel. High Octane fuel will not make you go faster but it will burn a little cleaner and IT WILL HELP PREVENT PREIGNITION AND DETONATION. In short, the lower the octane rating, the lower the temperature needed to ignite the fuel. So if your engine is running HOT then the fuel in your cylinder might ignite from the excessive temperature of your engine before the spark plug ignites it, OR if it's running HOT it can spontaneously ignite AFTER the spark plug fires which interupts the flame front from expanding evenly which yada yada yada. If you run racing fuel than you greatly reduce the risk of these problems. However, not everyone needs to run racing fuel. If your motor is high compression then I would recommend it, but if it's 80 degrees and your squish band is 6.0cc or larger you can probably stick with 91. I personally run 110 leaded at the track and 91 if I'm riding anywhere else. Ahhh, the smell of racing fuel alone is worth the extra $.

-Leaks. This falls under tuning but I just want to make double sure that your not running lean. If you have a leak, fix it.

Now that we've covered basic preventative measures for heating problems let's move on to mechanical problems that can easily be avoided.

- Check all bolts, screws, cables, levers, studs, etc. Make sure everything is tight and secure. If you don't want it coming out then consider using LOCTITE. Blue Loctite for things you would eventually like to remove, and Red Loctite for things you don't want to remove. This isn't absolutely neccessary, but it IS neccessary to pay VERY close attention to everything. I use Red Loctite on the head studs and Blue anywhere else, I dunno maybe I used Red on exhaust studs, I can't remember lol. But I do remember one thing for sure...

-I replaced all my studs with Grade 8 studs. It would suck if you couldn't finish the race because your intake stud came loose or broke. If you pay close attention to installing the bolts properly you can get by fine without doing this, but I wouldn't know because I changed all mine out asap. Let me interject here and point out that you might be thinking, "Damn, this is hella stuff." Well, let me remind you that you are totally capable of bringing your beater and doing well, but all this is here to help increase your chances of finishing. And after all, don't forget you are now a racer and it's now in your blood to do everything it takes to win. As if I needed to tell you! Lol

-Check chain alignment and chain tension. Make sure when your going over your bike, hopefully not any later than 2 weeks before the race(to allow shipping time for any last minute parts orders), that the chain is in perfect alignment and the tensioner is secure. Actually I recommend removing the stock chain tensioner, shortening the chain and running straight chain if you have adjustable rear dropouts, which I do not on my Trek Aluminum Mtn Bike, so I use a spring tensioner mounted on the clutch plate, similar to the TurboBuick Spring Tensioner, or others available from other manufacturers.

-Ditch the ragjoint sprocket mount and get a billet aluminum sprocket hub adapter. All your constant throttle on and throttle off is not nice on your spokes. Hub adapters are only $50 from Cortez Motorsports(Angel Cortez on Fackbook) and come in a 2" size with shims for 1.75" and 1.5" hubs available seperately. Also this makes changing sprockets really easy so you can quickly take off your 36T that you use on the daily and throw on a 41T or 44T for the track. Changing sprocket sizes is also something you might want to do during practice. that we've covered those mechanical issues let's move on to some goodies:

-Tires!!!! It is such an unbelievable difference when you run good racing tires(Slicks). There have been many people running stubbies on the track and eating it, or running skinny tires and eating it. If you come to your first race and crash and break your bike and hurt yourself you very well may not want to race again lol. I might regret this later when your passing me out the corner exit, but Maxxis Hookworms are regarded as one of the best, however there are nearly as good, cheaper alternatives such as the Cyclops CST. The 1st time I attended a race at SMBR I was running some cheap "slick-like" tires from Amazon and I fell 3 times off my bike when the sidewall gave way each time and I skidded out of control. Good tires were the 1st thing that I got after that and I didn't once feel the tires I chose begin to lose any traction in my last race. They went as fast as I wanted and were CRITICAL in my 1st place victory. As you are on the track in the 2 Heats you can experiment with different PSI's until you find the one that best matches your riding style and offers the best traction. I'm not telling what mine were at!!! lol

-Protection. At the race track you are pushing your bike and yourself to the limits, corner after corner, striving to find and maintain the edge of control and push it further, so naturally there are always a few people that go down. Good gear provides the ability to get right back up and into the race. I wear a good motorcycle jacket, full face helmet, knee + shin pads, high top boots and gloves. At my 1st race I somehow ended up doing the superman off my bike into a head first home plate style dive, sliding, and springing up to get right back on it like it was nothing

-Brakes!!!!!!!! Lots of exclamation needed here because I assume your not just riding your racing bike at the track, but also on the street as your getting ready for race day. It is of the utmost importance that you do not become a vegetable for your parents(or spouse) to take care of for the rest of your life! It is nice to be able to walk, and talk, and eat, and be alive. And I assume you enjoy being alive because your a racer, and racers just know how to live life real good like lol. So throw on a front disc brake, and don't skimp on it. At my last race I found my front 160mm rotor with mechanical disc brake to be good enough. However, it was not neck and neck racing so I didn't need every advantage I could get. If it was neck and neck, and my opponent had a 203mm front rotor with a hydraulic brake, then they would've had an advantage. I know this because I test rode another racing bike that had a 203mm rotor in front with a hydraulic brake and it blew my mind what kind of stopping power I was missing on my setup. That's the kind of thing that can mean the difference between 1st and 2nd, or alive and dead. So please, put on some really good brakes. You'll be very happy you did.

As we wrap up I would like to now address what is the most important key to winning. Practice. Practice improves lap times more than any performance part will. Rider skill is the cheapest and most effective upgrade. Attending the practice day before race day will give you a big advantage, because while others will be arriving and tuning their bikes and learning the track on raceday, you will be relaxed as you dial in the finer adjustments and methodically increase your corner entry and exit speeds. Usually SMBR is on a Saturday with an open track practice day on Friday, followed by a cool camp out Friday night where racers shoot the **** and crews from all over the country hang out. The testing and tuning you accomplish on Friday can make you much faster in the Final race. Friday is also a good time to ride the track with an experienced racer and learn their lines.

To finish I would like to add that porting the engine is extremely important if you want to be competitive. Other upgrades help a lot such as a bigger carb and expansion chamber, but watch out, because a big expansion chamber can quickly bump you up into the next class up. So pick your performance upgrades wisely, my bike was the fastest bike in the beginner class and it still had a stock NT carb and stock exhaust. Porting and tuning combined with the right sprocket size and good tires and brakes will set you well on your way to racing with the front of the pack.

Here's a quick upgrade parts list for the beginner class:
-Aftermarket head
-Sprocket Hub Adapter
-Short billet port-matched intake manifold
-B8HS spark plug
-High Quality 2stroke Oil
-Racing Tires
-Hydraulic brake w/ 203mm rotor in front

Do not forget these spare parts on your packing list:
-Spark plugs (different heat ratings)
-Head gasket

See you on Sat Oct. 17th at Grange for the next Socal Motor Bicycle Racing event.

Happy Racing!
Racing is an experience you will never forget, and unless you get run over you will cherish the memory always
Here is a race hardened build that will be racing in the Novice China girl class on Oct 17th.

#808 Dan Keltons bike nearly race ready.

New bigger tires (20x2.3), 18mm carb (Had a 16mm, don't ask why I didn't go 18 from the start), New tach and temp gauges and new style fuel tank.
Changed gearing from a 25t to a 28t, may need to go back to the 25 after a few test laps.

Is the engine angled off to the right to avoid the frame?
from what motorcycle is the pipe?
Is the engine angled off to the right to avoid the frame?
from what motorcycle is the pipe?
The engine is straight up and down.

You are looking at a custom welded perimeter frame made to fit that small
20" wheel frame.
There is the same top bar on the other side of the engine.

The frame is made out a a couple of bikes welded together.

That is a cut and rewelded pipe from a moped.
Can that bike actually be or peddled? From the picture it doesn't appear to have pedal clearance.
+1. I'd call that a motorcycle that happens to have pedals.The only snag I see with the races, you'd have to go to socal, I can make fun of it, I grew up there.
It's a drag you guys didn't keep the races to an actual bike thing, where the only mods you could make were to the bike, not the add on engine/trans, so the fit guy with the crazy small last sprocket would be top dog.
+1. I'd call that a motorcycle that happens to have pedals.The only snag I see with the races, you'd have to go to socal, I can make fun of it, I grew up there.
It's a drag you guys didn't keep the races to an actual bike thing, where the only mods you could make were to the bike, not the add on engine/trans, so the fit guy with the crazy small last sprocket would be top dog.

thats what the beginner class is for. I'm a small engine guy, not a bicycle guy.
Can that bike actually be or peddled? From the picture it doesn't appear to have pedal clearance.
Appearances can be deceiving.

Functioning pedals is one of our 3 or so rules.

Of course it can be pedaled. See how that moped pipe has been cut
and rewelded so that the pedals clear.

It would take a very foolish racer to even want to build a non pedaling
bike for this class of race bicycle.

They would be left for dead at the starting line and have a big disadvantage
coming out of the tighter corners at the go kart tracks we race on.

The motorized bicycle racers pedal their ass off!

The few 20 hp Unlimited class bikes are the only ones that don't need to pedal
but they still have to have functioning pedals to be officially scored.