how do i get my bike ready to race?

[skycr250]

i have a 1986 cr 250. i did a port and polish job on it. new piston. fmf silencer and pipe and all new tires. i jetted it down because of the elevation and have fly alumasteel handlebares. i don't know what to do to make it so it can go faster. i raced my friend on his 92 250 with an oversized piston and tied him and have raced new bikes and have had the same results. what should i do to my suspension and how? what should my sprocket ratio be and do i need to get the suspension worked on? thanks

 

[cr85rb_rider]

Id imagine 1986 suspension are pretty far behind todays suspensions, with a better suspension or with it tuned you could improve stability and turning, and with a new suspension you wont bottom out as much. As far as sprokets are concerned, ive heard drop one size on the front sproket or go up a few on the rear sproket to improve acceleration.

 

[skycr250]

alright i'll try getting my suspension dialed in and see what happens. i have one last problem but i have no idea how to solve it i've tried everything. As my bike is an 86 i sanded it down and repainted it the original color. but on the gas tank it just bubbles up. i've used everything from acetone to alcohol and nothing works. what should i do to prevent it from bubbling. someone said that there is wax on the tank and you have to sand it but i tried that and it didn't work.

 

[rushy08]

dont paint the tank. the vapours off the fuel escape through the sides of the tank and make bubbles. Thats why when fuel tank stickers are put on they bubble up.

 

[rmc_olderthandirt]

the paint on your gas tank isn't going to help you go faster. If it is a platic tank, leave it unpainted! Put your effort into work that will help the bike perform better and survive, don't worry about cosmetics on a 20 year old bike!

If you want to be serious about racing then you have to understand that the work you need to do is NOT a one time thing, it is a continuous process. A serious racer will definately change his suspension settings for the track. Air pressure and even tire changes will be made to adjust for changing track conditions (how wet the track is, the soil conditions, etc.) Some will even rejet the carb between morning and afternoon heats.

To be effective in suspension adjustments you have to really understand what the adjustments are and how they effect your ride. It is NOT an exact science, and there is no "correct" setting for the bike, but there is a "best" setting for you riding that bike on that track. Change the track or the rider and the suspension may need dramatic changes. If you understand the suspension (travel, rebound rates, bottoming out, etc.) and you can make note of it as you are riding then you can make a few practice runs and dial it in. Another approach is to make a small change and take another practice run and time the lap. Adjust, try it, adjust, try it, etc. Find the setting that gives you the best lap times and use that for the race.

Same with gearing. If you are riding on a track that has a long straight stretch you will want gearing that will give you top end. On the other hand, if the track has a series of turns and jumps that has you constantly shifting between 3rd and fourth you might do better to gear down and just stay in 4th. Again, it is rider preference and track dependant.

If you want to go faster for the least amount of money then study the suspension and what tire air pressure will do for you.

If you are willing to spend a little bit of money then get a selection of front and rear sprockets plus the tools to "break" the chain (you will need to add or remove links to adjust for sprocket size changes).

Learn how to "read the plug" and be prepared to change jetting, sometimes even throughout the day to adjust for temperature changes.

Or, don't sweat the details and just have fun racing your buddies. Accept the fact that speed costs money, and there will always be those who have more to spend than you do.

Rod