I have a gsxr 400r sp (gk73a model) and I have seen advertised that you can buy new cdi boxes that will increase power etc. Does anyone know if these products are suitable for my bike, or even if one make would be better than others. I have contacted the manufacturers (usually japanese) who just tell me it will fit a 1989/1990 bike, however this could be a gk76, not mine. Does anyone have any experience they could share with me.
thanks

If youve got the SP it should have a higher reving cdi ( about 1000rpm) so you may not get any gains. You could maybe get a programmable custom job.
The info youve been given about the cdis is bad as in 89 they made the gk73a RK and in 90 they introduced the gk76a RL.

thanks for your help. All this is a bit of a learning curve for me. I've had bikes in the past,but they have always been quite new and not needed any work. However my gk 73 is a different matter, I'm slowly trying to mint it on the grounds that is just as much fun to ride as my old zx9.

Ye! ive had loads of bikes but just love my Suzi 4 as i can have loads of fun and use all the bikes power without going banzi like the bigger ones do. Does the bike go about 120mph? as they came from Japan with a 180kph restriction, theres a green/yellow wire that goes from the gear selector near the front sproket up to the cdi.

be careful when playing with a 73a sp as alot of them came from factory with no limiter. There are other cdi's but the cheap copies are of no gain at all. They are a copy of a std cdi and bad copies at that. If you want more power then the best way is to look to more cc's with a 400. All other gains will be of no use on the road.

when you say more cc, do you simply mean boring it out, and if so do you then have to start doing work to the carbs etc. Also I would put a picture of it on here, but I cant seem to get the picture from my pc onto the site.

just a rejet nothing major.