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You could say I am sort of a slacker, or that I am just in touch with my machines, but I just knew it was time to do a major tune-up on my little 300. I got my bike new in April of 2014 and I feel I am pretty on top of preventative maintenance and general maintenance, but I am one of those that doesn't feel a need to rip the engine apart every few thousand miles to check on things if things are in line with expected performance. So needless to say, I have not done a valve job in the 6 years I have owned the bike and I have just short of 30,000 miles on the OD. A few things made the need for a valve job apparent. One, there was no typical valvetrain noise like tics or rattles and the bike was just starting to get hard to start. Another side effect is reduced power and gas mileage, of which both were becoming evident. I went from 230 miles per tank down to nearly 200 miles per tank. I could go to a top speed of 115MPH indicated before, whereas now I was lucky to break 110MPH with a tailwind and heading downhill. It was time.....

So how far off were my valves after 30K miles of flogging it around? Well interestingly, the intake valves were all identical and technically within spec. Mine measured at .15mm for all of them and spec calls for .14 - .25, so I was right there. The exhaust valves on the other hand ( usually the most egregious ones ) were probably ready at 15,000 miles to be adjusted... A little late on those I suppose. Mine measured out at .13, .1, .08 & .08 respectively and spec calls for .22 - .29! Yeah, just a weeeeeee bit tight! I removed the old shims and they all measured out to be 2.80mm, did my math and ordered a Hotcams kit. Installed the new shims and got the measurement right on the first shot! Buttoned her up and we are off the races.

I figured while I was at it I may as well go ahead and do some other mods and see if I could improve the odds for performance. I took out the airbox so I could remove the flame arrestor, drill some holes in the box and see what was going on in there. Let me say that getting the airbox out is a HUGE PITFA..... Don't do it unless you are already in need of removing nearly every fairing the bike has. I was looking at the snorkel and can say for sure it is a pinch point in the intake tract. The two holes it has are not bigger than your middle finger and you can't convince me it will flow all the air that the two cylinders want at 13,000RPM's. Next is the flame arrestor. The holes in it are very small and while it may not be a large hindrance to airflow ( it is ), it certainly isn't helping anything. I am shocked that more companies have not capitalized on velocity stack inserts for these things? The airbox has two rubberized velocity stacks ( typical of most bikes ) that are relatively long. This is good for low-end power, but different sizing could unlock some power. Generally smaller velocity stacks improve top-end power. This is why POD filters lose low-end oomph and gain more top end. I feel that a medium-sized velocity stack could bridge the gap a little and get a little more all around, especially if the airbox is free-flowing. I drilled several 1" holes ( 6 to be exact ) and the intakes limitation is no longer the airbox, but the air filter and or the secondary throttle plates.

About those secondary throttle plates. As best as I can tell they are not really as much a problem as we would like to think they are. They are a 40mm bore while the actual primary throttle plates are 38mm. So even when only opened up to the supposed 92% ( the number I have often seen referred ) they are flowing as much as is needed to feed the engine its air. My feeling is that the secondary plates are purely designed to manage power delivery at high load wide open throttle situations. It makes sense to me why most airbox and filter mods don't do much. The stock intake isn't restricted until well into the upper rev range and the STP's manage the air needs at lower rpm's to improve throttle response and power delivery. So opening the airbox up doesn't hurt things as much as it helps and my test drive after getting things back together seemed to support that notion. My point being, that even if the STP's are a fixed map, it will do what it does at lower rpm's and the free-flowing airbox will allow more power to be built in the top end. I also think that leaving the stock velocity stacks helps make the stock fuel map work better than throwing a POD on the bike. My test ride was very nice and power delivery was buttery smooth and didn't have dips or humps in the power delivery. Just a very smooth and even pull all the way from a stop up to as fast as you care to go.

To clarify what I did to the airbox. I drilled 6 X 1" holes ( on the intake side of the air filter of course ), installed a K&N air filter and removed the flame arrestor. I left the rest of the airbox alone of course. I do not have a fuel controller and I was a little worried about how lean the bike may be after the modification, but it struck me that the bike must have at least some sort of way to meter air flow and upon removing the spark plugs, it showed to me that the bike was running a tad on the rich side anyway. I still have the stock exhaust so I wasn't that worried anyway. I did hack my airbox up after all. I think that if you are on the fence about going with POD filters, a better alternative if you don't want to spend money on a fuel controller and subsequent dyno tune, is doing what I have done to the airbox. It is as close as you can get to PODS and NO peripherals are needed. My bike responded very well to this mod. Oh, and the intake noise is glorious too BTW! It howls, screams and almost makes the bike sound like a V4.

Beyond the engine is the brakes... I have always been less than happy with the front brakes, but again, if it isn't broke, no need to fix it. Well, my stock brake pads were finally up for replacement. I went with EBC HH pads to replace the stockers and they definitely improve the braking. The initial bite is better and they grab more in general. I have a stainless steel brake line arriving tomorrow and I will report back once that is installed. I can feel the stock rubber lines expanding with what is the typical brake lever pressure needed to bring the thing to a halt, so SS lines should greatly improve feel and reduce some lever travel. My biggest gripe about the stock system is that I could nearly squeeze the lever all the way to the bar and still not feel like I was slowing down. The EBC HH pads at least feel like they would lock the front up if I went ham on it. I think the stock master cylinder is perhaps a little oversized for the caliper on the bike? It seems a large part of the energy exerted is moving more fluid than is needed and trying to make the stock organic pads do some actual clamping. Once I get the SS line on there I will know more.

All in all, I am so glad that I finally did a major tune-up. For spark plugs, I went with the NGK CR8EIX ( iridium ) and I can't say that they are better or not, but the stock CR8E's were definitely done at 30,000 miles with a gap of .50mm! Perhaps the valves and spark plugs will fair a little better until I get to 60,000 miles? The airbox mod was very much worth the effort I think. My butt dyno says it was a good choice as I don't feel surging and overall sluggishness like I did before ( even when the bike was new ) and the power delivery is now smooth and buttery. Responsiveness is improved and the intake noise is very nice. We already knew the stock brakes suck and the EBC HH compound is surely worth the $36 investment. If you have made it this far into my post, thank you and I apologize for not having pictures. I am just not the guy that takes pictures every few minutes while my hands are all greasy. I will update later with video and pictures of some sort. Take care and ride safe everyone.
 

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I'm doing the valves now. I wish I knew what 'a low resistance means'. When I push in the gauge I feel an initial resistance and then it slides much easier. But I guess is from the angle of the gauge. I guess I have to consider the gap after the gauge 'came in' and the gauge is bent and sliding horizontally.

I also found my intake valves in spec and my exhaust valve tight. 15k miles on the bike, first valves check. All exhausts gaps are around 0.17mm and should be around 0.26
 
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