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Discussion Starter #1
So I'm experiencing a problem and I need help diagnosing it. It started about a month ago after I installed a pc3 and put in thicker oil for the summer time, I went from 10w-40 to 20w-50. It only happens in 2nd gear between 9k-11.5k and only if I'm WOT. If it's anything less throttle wise then it doesn't do it and it doesn't do it every time. Now what I'm experiencing is a skip or jump. The best way I can describe it is like if your chain skips a tooth on your sprocket. It doesn't bog, shut down, but the rpms jump 500-1k rpm and then return back down when it engages or catches whatever it does after it skips. I'm a mechanic at a shop and my boss doesn't think it's the transmission but something tells me it is. It's not the pc3 cause I took it out and it still happened. I have fellow friends who are knowledgeable about bikes telling me it could be my tps, a sensor or transmission. My boss thinks it could be a cam sensor or something electrical. What do you guys think? My bike has 44,700 miles on it.
 

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But if it was the clutch wouldn't it do it in every gear? Not just in 2nd gear, right?
Just sounds like something slipping, and that's the first thing that comes to mind. Torque will be different in each gear, who knows?
 

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Discussion Starter #5
True I probably could use a new clutch and clutch springs from wheelies, a couple track days, and as my daily vehicle. I bought her with 20800 miles and I was never told the clutch was replaced and I sure haven't done them yet. So maybe.
 

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Can you provide some data or anecdotal evidence that using thicker weight oil for higher temps is commonly accepted? Here in socal they race 100+ degrees in the desert and I haven't really heard of racers changing their oil weights from what is specified. I don't think that the higher oil weight and near 100% constant humidity could be doing weird things to the oil bath of the clutch, but... it also could be.
 

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Discussion Starter #7
No I just thought using thicker oil for the high heat would be better lubrication. I could be wrong but I don't think the oil is causing my issue cause it only happens in 2nd gear between 9-11k rpm and only at WOT.
 

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Yeah, and I also don't think it's the oil, I just wanted to float the idea.

If a clutch has lived a hard life, it could be slipping at 44k. Traditionally the only things that could beat up a clutch so bad to do that are race starts, and stunting. (clutch up wheelies)

And correct me if I'm wrong, but there isn't just one clutch plate like in a car, but several clutch plates in the pack that each have their own friction surface, so you could have one be slipping but others be okay.

It seems like replacing clutch parts aren't too expensive, so it could be for the best to refresh them.
 

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Discussion Starter #9
Yeah, and I also don't think it's the oil, I just wanted to float the idea.

If a clutch has lived a hard life, it could be slipping at 44k. Traditionally the only things that could beat up a clutch so bad to do that are race starts, and stunting. (clutch up wheelies)

And correct me if I'm wrong, but there isn't just one clutch plate like in a car, but several clutch plates in the pack that each have their own friction surface, so you could have one be slipping but others be okay.

It seems like replacing clutch parts aren't too expensive, so it could be for the best to refresh them.

Yea I bought the bike at 20,800 miles and I had my wheelie phase (clutch ups) and recently did 2 track days besides numerous drag strip runs. Since I work at a shop my boss thinks it's something electrical since it's consistently happening around the same time.
 

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None of this happened until you changed the oil and went with a heavier weight, correct?

Did you stay with the same oil brand/type/etc. or did you change that as well?

With that many miles on a bike that's been ridden hard I would not be surprised the clutch is "questionable" and the change in oil is bringing that to light. Simply changing from 10w40 to 20w-50 shouldn't CAUSE a problem, but might bring something up.

The symptoms are classic worn clutch; not transmission, TPS or something electrical or it would be far more abrupt or more of a shock type thing. It's not unheard of to only have slipping in one gear or rev range because of load placed on the clutch at those times; and honestly how often are you in 3rd, 4th or 5th pushing 9k WOT on the street?

You have a few choices at this point, your call.

- Easiest and cheapest is to change the oil back to a 10w-40 and see if that fixes it or makes the symptoms disappear. $40, no need to change the filter, but pull it and dump it, get all the old oil out. It may "fix" it but prepare to replace your clutch soon if it does.
- Pull your clutch cover off and look at the plates, both metal and fiber; replace if necessary. $175 or so, I suggest OEM, but EBC, whatever quality aftermarket will work fine. You might just need fibers so pull them and inspect before ordering. Most modern bikes have plates in a specific pattern and placement for plates, KEEP THEM IN THE SAME ORDER AND ROTATION ACCORDING TO THE MANUAL.
- take it to a shop with a dyno, have them recreate it and see what they think.

I've done all the above and had all the above work for me on various bikes Over the years.

Mike
 

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Discussion Starter #11
Yea all this happened after I put in the thicker oil and installed my power commander. But I took out my power commander and it still did it. Yea I used the same brand of oil. Funny thing when my boss and I dyno'd my bike last Friday we couldn't get it to do it on the dyno but as soon as I left work I did it hoping the tune fixed the problem and nope it jerked. So i don't know if that's cause the dyno doesn't have the same resistance as the street or what. But Im do for an oil change so I'll change it back to the 10w-40 and see if it goes away. I was planning a clutch replacement as well since I'm sure it's getting there. Plus I don't know if it's ever been replaced before me..
 
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