GSX-R: Strange symptoms, hard to research and find cause

[Blitz]

So, I've been working on getting my bike in peak condition. For the past month or so I've noticed a couple things and I don't know if they're connected and I'm having a hard time finding the cause.

First, the bike has been hard to start when it's been warm. If I pull over and the bike is over 190 degrees, it will turn over but not fire. It acts like it wants to fire, and eventually it will. But it's hard to get it to start. If it's cold, or if it is ridden and kept cool and the bike temp is 170 or a little over, it starts just fine.

Secondly, this may or may not be connected, it seems like there's been a sight loss of midrange power. It seems like at 7k RPMs, when I get on the throttle hard, it normally would quickly wind up and go. But lately it seems like it's hesitates more at this rpm than before. There's no bogging down, like fuel related bogging. And it doesn't cut out or hesitate. Just like there's less power.

I'm planning to take off the PC3 and see what that does. My other thought is that the valves need adjusted. But I would prefer to wait until the winter and do the valves myself than to pay someone a lot to do the valves now. And I would like to know that the valves are the issue before I have them done and it still doesn't start when warm.

I've read that the temperature sensors could be the problem, as well as the starter.

Anyone have any ideas? Anything I should check?

Edited May 24, 2015 by Blitz

[Gixxus Christ!]

First thing that comes to mind is vapor lock or the gas basically boiling out of the fuel rail from engine heat. Try this: go get her on boil, then shut the motor off for a while, then turn it on and off half a dozen times so the fuel pump runs it's prime cycle a bunch of times And see if it starts right up. If it does, you may just need to put a heat shield on your fuel lines. A bad sensor would likely throw a code but it's easy to diagnose the sensors, just need to look up the resistance values and check the sensors with a meter when the bike is hot. As far as your flat spot is concerned I don't think valves are responsible but if they are due, they should be done. It's not a super hard job, but the cams will need to come out if any need adjustment. Not a hard job but definitely labor intensive when you consider that you need to pull off all the plastics to get to the motor.

[Tonik]

Have you tried cracking the throttle open a little when it's hot and is hard starting? Fuel injected? If yes are the throttle bodies clean?

Edited May 24, 2015 by Tonik

[Blitz]

I have tried cracking the throttle and that usually helps. It is fuel injected, so I shouldn't have to do that though. Right?

I have not cleaned the throttle bodies. That a good place to start?

[Tonik]

I had to crack it on my last bike. Yes, cleaning the throttle body is a good place to start.

[ScubaCinci]

I was thinking valves as well...what is the valve check schedule and how many miles on the bike?

[Bubba]

I think you and others may have hit it on the head--valve clearance.  If you haven't checked them in 5-6000 miles, that'd be where I'd look.  Difficult starts and reduced power when hot is a sure symptom of overly tight valves, most likely the exhaust valves.  You could prolly check the compression cold vs hot to get an early diagnosis, but as long as you're pulling the body work and other parts off, go ahead and set 'em while you're in there.

Edited May 24, 2015 by Bubba

[Blitz]

So, here's what I did:

Pulled the Power Commander 3. It was on when I bought the bike. Have no idea what the map is or whether it was even dyno'd. I don't think it was.

I also cleaned the throttle bodies. They didn't seem all that dirty. I mean they made a handful of q-tips pretty gross. But nothing in there seemed like sludge. Just like a fine film of what...varnished fuel?

Anyway, I took the bike out and immediately noticed that the hesitation that existed when letting out the clutch in first gear was gone. It used to almost stall out from a dead stop up to ten mph in first. That was gone...smooth acceleration. Then it ran like a bat out of hell through the midrange. Faster than the bike has ever ran. I mean I was screaming in my helmet cause the change was so significant. Then I let it get hot 5 or 6 times and it started up fine every time. Yesterday when I ran a can of sea foam through it and replicated the failure to start hot issue, I could do it every time. Today after the throttle body cleaning and PC3 removal, I could not. So it seems fixed.

Now, I don't know if it was the throttle body cleaning or a bad map on the power commander that was the problem. That's the next thing I'll have to find out by hooking the PC3 back up.

Valves still need checked because it calls for it at 14k miles. It has almost 30k miles on it and I'm pretty sure its never been done. But having never done it, I'm not sure I want to do it myself.

Nonetheless, thanks guys for the help. I'll post up what I find after I check the PC3. I'll really be amazed if it was the throttle bodies that caused such a significant change in how it's running.

[MidgetTodd]

Put it on and take to Brian.

[jacobhawkins]

What did you have done at pony? Just the forks?

[whaler]

Power Commanders also seem to fail regularly. A bad map will not work fine for years and then not work one day. Forget the PC and ride it.

[MidgetTodd]

Fail regularly? I've had them on every fuel injected bike I've ever had, most everyone I ride with has. I'm with Brian regularly who tunes them daily. I've yet to hear of one fail let alone regularly. PC problems are with the programmer. If you say forget it and ride then you've never had a properly tuned one. Put it on and have Brian tune it, night and day difference.

[Blitz]

Yeah, just the forks Jacob.

If I remember, the guy I bought the bike from said the map was downloaded. I've looked and there aren't any maps available to download that use the same exhaust and air filter, let alone being custom to my bike. So, it's not surprising that it's running better without the PC3.

Plan now is to make sure the valves are within spec and then have it dyno'd.

[mango_sv]

Get that thing to a dyno. My SV was the same way on the downloaded full M4 maps from DynoJet. When I got it tuned, it was off the charts rich in the low end. So much fuel it was choking the hot motor.