Ask Sparks Racing

Dear Curtis
I own a 99 EX and seriously want to hop it up…..I have researched the .40 over kit some but I can’t find much on the .90 over. I know that I will have to bring in an oversized cam and replace the carb. I also plan to run it with a complete aftermarket exhaust, and change the rev limiter. What can I do to keep it running as cool as possible. I have seen larger aftermarket oil coolers but can’t find more info on them. What is your opinion? Is this too much of an increase to expect decent engine longevity? I run some MX, dunes and flat track. I have already put on a K&N air filter and have modified my air box for more airflow. Is there anything that I’m missing?

A big bore kit for the 400EX will make it run stronger, no doubt. There are some steps that are recommended to increase the reliability of the motor. First off, when a larger piston is installed the crank and rod become a possible weak link. I don’t want to say that rods are snapping right and left, but there have been motors as small as .80 overbore break the stock rod. There are aftermarket rods available that remedy this problem. Also, the crank halves have been spinning on the crank pins when the crank is not trued and welded. All of this is also affected by the compression ration of the overbore piston. The clutch can be beefed up with a better clutch fiber, steel and spring kit. It would also be a good idea to consider the Hinson clutch basket. The heat problem with the 400EX is caused from the cylinder being air-cooled, not because the oil gets too hot. Higher-octane fuel is the only way to make a dent in the cooling of the 400EX. That is also why alcohol is a good idea for some motor kits. There have been some head studs pulling on a number of motors from the heat. If you run a K&N, (which are great for allowing maximum air flow), make sure to run an oiled foam filter around it to catch all of the fine dirt that the K&N won’t catch. There are ton of options for the 400EX, make sure you make a smart plan of attack that takes reliability into consideration.

Dear Ask Curtis Sparks Racing,
Where could I get more information about Matt Coulters machine?

Matt’s has several quads. The one he used last year to try to break his distance record with was aPhillips frame with a KTM 525 two stroke dirtbike motor in it. He uses this same set up with a 250cc motor for most of his stunts and shows in England.
Check out his website for more info. www.kangarookid.com

Hi Curtis,
I’m new in Vero Beach, near Orlando. I’m 18 and I want to get a new bike. I have had a Blaster and a Warrior in the past 5 years. I saved up some money and I want to know if I should get a Banshee or a Raptor. Which will be the best for my area.
Thanks.

Well, you know that we are fond of the four stoke power plant. We have been very impressed with the Raptor motor and its potential. Any time you make a 5-valve, water-cooled, four-stroke engine, you can have some fun. Once you install an aftermarket exhaust, jet kit, and air box on the Raptor it will run like you’d hope that it would out of the box. It is a powerful motor once it is allowed to breath. Of course the Banshee has been around for a while and the two-stroke twin motor can produce a bunch of peak power. I would say that Raptor would be easier to ride and the Banshee would be a better hill shooter. The Raptor has better ergonomics, but both chassis need some help. We would take the Raptor over the Banshee, but the question is, what is right for you?

Dear Curtis Sparks Racing
I have a 2001 blaster. I have many up grades but I’m looking for some motor work done to make it faster. I race Supercross and compete against 400EX’s. It sounds weird, but I can beat the other guys, but not by much. I was looking for something that it will give it more go power for under $1,000. What pipe is the best for that set up? Thank you for you time.

There are a few things that are available to help the Blaster. The exhaust is certainly a good place to begin. The carb and reeds can be improved and of course porting and head mods would make a really good gain in power. As far as which exhaust is best for the Blaster, make some phone calls and ask all of the companies what their exhaust can do for the Blaster’s power. Ask some of your friends what they know, and ask other riders with Blasters, maybe they have some experience that can help you out as well.

Ask Curtis Sparks Racing
I have a 1999 Honda 400EX. How well will the stock XR400 cam work with it? I have a UNI filter, vented air box lid (9 UNI vents) and have made a custom tip for my stock muffler without the spark arrestor. I do understand camshaft specs/selection but can’t find the numbers for my stock cam or the XR400 cam. The Honda cam is cheaper for me to buy since my Canadian dollars don’t work too well for me across the border. I also want to keep expenses down as I am waiting for Honda’s answer to the Raptor 660R. Your rev limiter box and advance key also looking very tempting, do they work well together? The key advances in the initial ignition timing is six degrees, and the CDI changes the ignition curve and the rev limiter if I’m not mistaken. Your suggestions/comments would be greatly appreciated.

The stock cam from the XR 400 would be a good item for the 400EX. It is a small step up in performance and can still utilize the stock rocker arms and valve springs. Advancing the timing six degrees and letting the motor rev another 1000 rpm is a good idea and they work well together. As far as Honda’s answer to the big bore four-stroke competitors, we are not so patiently waiting for it as well.

Dear Curtis,
I have an ’87 LT500R Quadzilla . It has been rebuilt from the ground up into a sand quad. Last week at Glamis I noticed a lot of white smoke coming from my exhaust. I figured it was the head gasket, since I had already had the studs stepped to 14 mm. I had not had a problem since. I pulled off my head and sure enough it was blown. Now I noticed the smoke right away and shut the bike off . I know I did not over heat it. I replaced the gasket and put some gasket cinch as some insurance. After starting the bike my smoke problem was gone but now when riding anti freeze comes out of the overflow tube. It is not boiling or steaming but just pouring out like there is a blockage. I put the head gasket on just how my shop manual told me. Could this be a bad radiator cap? The local shop says I could have warped my head but that is hard for me to beleive because there is no white smoke. Any help would be appreciated.

There is definitely a problem with either the head or top of the cylinder. The surfaces need to be made flat again. Find a completely flat surface and rub the head in circular motions over fine grit sand paper to get it flat again. It isn’t that uncommon of a problem and any good engine builder should be able to handle this problem if this doens’t work for you.

Dear Curtis Sparks Racing,
I recently put on an aftermarket pipe. They recommended I go from a blu/grn primary spring to their green spring, and go from a red to a blue secondary spring. I totally lost all top end so I went back to stock springs. The problem is prior to putting the pipe on my 95 sport would walk all over my 96 sport. Both bikes have aftermarket reeds, reed spacer. I want top end so what do I do? Is it time to change sprockets? My 95 runs a 34-rear, 12-front, my 95 runs a 34-rearand a 13-front. I was thinking about going to a 30-r, 13-f. I find it hard to believe that it killed my top end that much. I would appreciate your help, since I am pulling my hair out. What do you suggest? gearing, helix, etc? Thanks a lot!
Mike

One critical piece of information is missing, what bike are we talking about. When asking a technical question, please provide as much good information as possible. We do need to know stuff like what bike, jetting, bore sizes, etc. We don’t need to know that you bought from your buddy down the street and you can jump it 400ft while doing a nac-nac. Sometimes it is tough to know all that we will need to know, but try your best.

Curtis,
I read some of the letters you received about the 400 ex in regards to performance and I want to change my exhaust and a few other things. I read something about the rev limiter (comp box), could you explain a little about this. You also said something about your own exhaust pipe, does that include a header also. If I wanted to order the pipe and comp box along with the air box. What would it cost me to order it from you and will this bring the bike alive.
Thank you for your time and this great column!

We would love to tell everyone how great Sparks Racing products are for your quad in this column, but we try to keep the questions non-brand specific so that it is fair to everyone. The 400EX responds well to a complete exhaust, (headpipe included). The high rev CDI box that is available from several different companies allows the 400EX to rev about another 1000 rpm (9300 to 10300rpm). The 400EX could use that in most situations. The one down side to this box is that it is hard to start when it is really cold out and the motor has no heat in it. It is easily started with the stock CDI or by pull starting. Increasing airflow is always a good idea. Just make certain that motor is still protected well from dirt and that the air has time to settle down before it gets to the carb and nothing disrupting it as it flows. Think about aerodynamics, a smooth shape disrupts the air less than sharp edges.

Dear Sparks Racing
Hello, I have a new 350 Banshee and I want to race on quarter mile shale ovals and tarmac short circuits in England and Ireland. I have fitted aftermarket pipes, big jets, air box mod and rear link-lowering arm. Without spending a fortune I need to get the front suspension lowered and choose some wheels and tires with suitable offsets and tread patterns. Do you recommend smaller front shocks or chassis modification to get the front end lower? Should I run an anti-roll bar? What shocks do you recommend? Do you put a “wedge” in the chassis for ovals? We used to race F1 stockcars (similar to your World of Outlaws. sprinters) so we have some idea about the ovals. I’m afraid these questions are elementary but that’s where I am right now! Many thanks for your help-Top website!
David King.UK.

We don’t really race the Banshee much under the Sparks banner, but all of the things you mentioned for the chassis are good ideas, but they are good ideas for the Sprint cars. Wide and low is a good rule of thumb and a swaybar is great for keeping the front end down, as it will allow the front suspension to work as one. As far as specific recommendations on the chassis, I would contact one of the companies that have experience with TT racing here in the US. Shane Hitt uses PEP and Jeremiah Jones runs Custom Axis.

Hey Guys,
I have a new Raptor that does not miss a beat when I blip the throttle. The problem I’m having is excessive vibration making your hands numb and knocking the fillings out of my teeth after only 10 minutes of hard riding. I have checked the motor mounts and they seem fine. What happen to the counter-balancer that is supposed to absorb the excess vibes? I’ve only had the bike for 2 weeks and it’s completely stock. When the dealer drove it around their 100 yard strip they could not feel anything abnormal. I don’t think they even got the bike passed 3rd gear. Please advise. Thanks.

The Raptor does have a counter balancer in it. We’ve seen it with our own eyes. We have also spent a little time riding the Raptor and don’t feel that it vibrated excessively. We’re not sure what your Raptor might be doing. Maybe find another Raptor rider and ask his opinion.

I will be buying a new ATV very soon. I’m 35 years old, 220lb and will be riding mostly in dense woods and racing hare scrambles (maybe once or twice a year). I love the EX’s styling and reliability but wish it had reverse. Should I just buy the Raptor or do you think Honda will have a reverse gear on the 2002 EX this summer? Any info would help. I keep going back and forth on this.
Thanks a bunch!
Richard

The Raptor is a great quad. It is a five-valve, water-cooled power plant that has a bunch of potential. The 400EX is a great overall package with a four-valve, air-cooled motor that can be made to run very well. We would give the 400EX the nod for the chassis and the Raptor the nod for motor. Which is right for you? It is a tough one to answer. We wouldn’t let reverse be the determining factor. Try to spend some time on both of them and your decision will be easier.

Curtis,
How about building a sprint car motor for the old 11x. I am his right hand man and that is all we ever talk about. We are having problems and I was wondering if you have ever thought about getting into sprints.

For those of you who don’t remember the 11x, — it is Greg Bakker’ s number. He is alive and well. He is a running a Sprint car now and has even been known to jump back on a quad from time to time. Greg was at the Tulsa TT shootout this winter and won the open pro class on his old Sparks 265 national motor.

Hi Curtis
I am going to be purchasing a 250R or a new 400EX soon, I know that the 250R is a two stroke. I am thinking of the negative attitudes with the 250R since I’ts used. I was wondering if I should rather get a 400EX or an R. What do you prefer? I will be doing a lot of dirt riding and woods riding. I want something that has power and racing abilities.
Thanks

The 250R is still definitely the best quad available for all out performance. The nationals prove that every time someone other than Tim or Doug wins. The 400EX has its strengths though. It can be bought new, the four-stroke produces a broad useable power, and it’s chassis is pretty good right off the show room floor. If we were racing again, we would run a 250R. For play riding, we would consider the 400EX pretty strongly.

I want to customize my Raptor this winter. What can I do to get the most power out of my machine without sacrificing engine life?
Thanks
Donny H.

The list of aftermarket goodies for the Raptor is growing fast. As far as the motor goes, there are huge gains to be found with a complete exhaust, jet kit and air box.

 

ATV Scene is proud of our collaboration with one of the most successful, knowledgeable and respected race teams in the history of ATV racing! Curtis Sparks has brought a lifetime of know-how to the sport. Before, during and now after his personal racing career, he has fine-tuned Sparks Racing’s products and services resulting in some of the best performance products available on or off the race track!

Here’s your chance to get your ATV to run like a top pros. If you have a technical question (or any other question) for Curtis or any member of the
Sparks Racing Team, simply click on the e-mail link below and submit your question. Your questions will be answered in upcoming issues.

(Please try not to aim your questions directly about Sparks Racing products. Instead be less specific so your question can relate to all ATVers – not just ones that own a particular Sparks Racing products).

Send your question to asksparksracing@sparksracing.com. For a look at what’s available from Sparks Racing, check out their web site at
www.sparksracing.com

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