cant go very fast

Some of you may have helped me in previous threads and I now have another question.

Recently found out that the inline fuel filter that was on my bike from the previous owner was backwards and starving the engine, removed it and now the bike starts every time, idles great, and no longer dies after a long ride.

My problem now is i cant seem to accelerate very well on the highway. when im going about 90km/h ( 55mph) in 6th gear i'm at about 6000rpm and that's about as fast as i can get it. I'm new to bikes but this seems pretty slow to me but i could be wrong. Also on the highway i noticed that if i give it too much gas the engine will bog down a bit.

now my air filter at the moment appears to be a piece of foam glued in to the air box. i know this is not ideal but im trying to source out a new box and filter. the exhaust is stock so im not sure if this piece of foam may be giving the engine too much air as ive read that these engines are pretty picky and you cant usually use anything other than the stock air box and filter.

Also wondering about a possible timing issue? contact points?

fyi, bike is a 81 kz305 ltd.

Any changes made to intake and exhaust will probably result in carb re- jetting . Solve the filter problem and then tackle the any re-jetting if needed.

Have you tried a tune up?

Plugs are new. What else would be part of a tune up?

Janz3n wrote: Plugs are new. What else would be part of a tune up?

If you have a Kawasaki Service Manual take a look in it. It not only contains the maintenance schedule; it also describes how to perform all the maintenance. If you don't have one I HIGHLY recommend you get one. It is pretty near impossible to properly maintain a KZ from a safety and performance perspective without the manual. In the mean time, below is the 1981 KZ305 Periodic Maintenance Chart from the manual. You should assume the previous owner did zero maintenance, and you should perform ALL the maintenance items, not just the tune-up stuff, so you can set a baseline from which to measure the maintenance intervals. Ed

well had some time to take things apart and im trying to track down a new air filter to replace the piece of foam. pulled the plugs and they look white which would explain why my exhaust pops on decel and the lack of power to get faster than 90km/h.

first, bought some new handlebars and grips so now im sourcing out all new controls ei. brake master, levers, headlight turn signal controls and throttle. also going to shorten all the cables and get stainless brake line.

anyways, on to the real problem. removed the carbs and disassembled them. I was going to check the float levels before i did this but i figured if im going to clean the carbs and fix them i might as well do that first. first thing i noticed was the diaphragms were full of holes and dirty. then i removed the float bowls and noticed a ton of dirt inside of these as well. so im happy to find that the diaphragms have holes because this would explain why i cant go fast, have a lean burn and why my exhaust pops on decel. another thing i noticed was after a long ride when i go to rev match around 4-5rpm it would bog along with some bogging a mid throttle.

so now im off to find some parts.

Well $230 and 3 weeks of waiting I finally got my diaphragms and installed them. Bike is like new.

Good deal. I know it sucks waiting on parts, but now that your set, you can get out and enjoy it.

the wait was one thing, the price for diaphragms was another.

You could think of it as a really good performance boost for $230! I can't imagine any aftermarket part that could offer that kind of bang for your Buck.