Bike won't rev past 8,000 RPM when cold

I have a problem that is just odd�

My bike will start up just fine, no issues. It even sounds good revving, except it hits what feels like a soft rev limiter at about 8000-8500 RPM�.just kind of bounces off it and won�t throttle past it. It rides fine, pulls hard, etc�as long as I stay under 8000 RPM. It behaves like this until about 150 degree engine temp, then its like a switch was thrown and it functions just fine, wraps out, etc.

My thought was the wax idle unit�did I possibly tweak something in my recent engine work? How can I check for correct functionality?

What's the problem? :unsure:

Shouldn't rev it high until it's warmed up anyway! :rolleyes:

[image: View Post]Tightwad, on 01 April 2010 - 05:41 PM, said:

I have a problem that is just odd�

My bike will start up just fine, no issues. It even sounds good revving, except it hits what feels like a soft rev limiter at about 8000-8500 RPM�.just kind of bounces off it and won't throttle past it. It rides fine, pulls hard, etc�as long as I stay under 8000 RPM. It behaves like this until about 150 degree engine temp, then its like a switch was thrown and it functions just fine, wraps out, etc.

My thought was the wax idle unit�did I possibly tweak something in my recent engine work? How can I check for correct functionality?



Vtech doesnt kick in till around 145 dgree, probably something to do with that. I've not tried the 8,000 rpm on a motor below 150 degree.

[image: View Post]Tightwad, on 01 April 2010 - 05:41 PM, said:

I have a problem that is just odd�

My bike will start up just fine, no issues. It even sounds good revving, except it hits what feels like a soft rev limiter at about 8000-8500 RPM�.just kind of bounces off it and won't throttle past it.

Not sure what you mean by "cold", but mine behaves like that in the winter when the temps are freezing and below. (Yeah, I pretty much go once I figure I have oil pressure.)

I can't tell you why about the revs but, most people measure engine temp by coolant temp. That is a very faulty measurement of engine operating temp.

It takes about 20 miles after full coolant temp for your OIL temp. to get where it needs to be. Cold oil and high revs don't go together at all. I hate it when vehicles don't have oil temp. gauges. :491:

[image: View Post]Bent, on 01 April 2010 - 06:39 PM, said:

I can't tell you why about the revs but, most people measure engine temp by coolant temp. That is a very faulty measurement of engine operating temp.

It takes about 20 miles after full coolant temp for your OIL temp. to get where it needs to be. Cold oil and high revs don't go together at all. I hate it when vehicles don't have oil temp. gauges. :491:


The reason I put significance on the coolant temp (which I realize is not oil temp) is that it is like a switch at 150 degrees. As far as I understand, VTEC doesn't engage in neutral anyway, right? So that takes the VTEC part out of the equation in my mind.

Incidentally...how many vehicles actually have an Oil temp gauge, and who knows what the right oil temp is?

[image: View Post]Tightwad, on 01 April 2010 - 06:55 PM, said:

As far as I understand, VTEC doesn't engage in neutral anyway, right? So that takes the VTEC part out of the equation in my mind.



Actually I think once vtec temp is hit it's vtec all the time? :unsure:

[image: View Post]Tightwad, on 01 April 2010 - 06:55 PM, said:

[image: View Post]Bent, on 01 April 2010 - 06:39 PM, said:

I can't tell you why about the revs but, most people measure engine temp by coolant temp. That is a very faulty measurement of engine operating temp.

It takes about 20 miles after full coolant temp for your OIL temp. to get where it needs to be. Cold oil and high revs don't go together at all. I hate it when vehicles don't have oil temp. gauges. :491:


The reason I put significance on the coolant temp (which I realize is not oil temp) is that it is like a switch at 150 degrees. As far as I understand, VTEC doesn't engage in neutral anyway, right? So that takes the VTEC part out of the equation in my mind.

Incidentally...how many vehicles actually have an Oil temp gauge, and who knows what the right oil temp is?


My VTEC will engage well before 150 degrees. I did it just to see if it would since everybody says it won't (am I contrary?). As far as VTEC in neutral, that sounds like a formula for disaster!!

The M3 I used to own had a factory and accurate oil temp. gauge and I put one on the Harley I used to have (I admit it, I'm so sorry.... :rolleyes: ).

From what I've seen with my 02 and read in the shop manual, there's a temperature sensor independent of the sender for the thermometer. It controls the VTEC system, and pops on 149F. I tried to kick it just over 7K below temp, and sure enough, the engine note didn't change, and it seemed a bit restricted. At 150F, it worked just fine, though the transition is a bit smoother at 175.
Why do you need to go over 8 grand when cold anyway? I don't pop VTEC a whole lot other than on twisty roads and stuff..

[image: View Post]Nelso90, on 01 April 2010 - 09:21 PM, said:

Why do you need to go over 8 grand when cold anyway?


No one needs to, he's just concerned due to a recent valve check ordeal...

It should still rev or atleast mine will even when cold and before the Vtech Temp point..

Something isnt exactly right although I cant help much with diagnosing it.. Posted Image

Oh, I didn't read where he said he adjusted his valves, (stupid iPod!). If you are running into what feels like a soft rev-limiter, then I'd say there might be an issue. But you have to consider too that w/o VTEC engaging, you have half the valve area. That would make an effect on how the engine revs, bigtime. I remember this being a problem with an old CM400 I had as a first bike. Wouldn't go over 4500 at all. I had to jet it a size bigger on the mains, then it pulled hard (for a 400). But the possibility of it being a fuel issue is kinda small with FI. Have you done anything with the ecu at all?

OK flame suit on...

Josh... mine's in ºC not ºF but I have so many times been far too impatient to wait for my '03 to warm up (thermostat is stuck open and I haven't had time to fix it) that I have just taken off (10-15 minute ride to work, and back)...

I usually try and wait until the temp gauge registers 36ºC, (under which it's just two hyphens)... and I take it real easy on her...

In my case the threshold temp for VTEC engagement is 64ºC (147ºF)... doesn't fail. Not one degree less nor one degree more. At this temp it's quite an abrupt engagement the first time round (or first few times even).

Just to dispell a few doubts...

VTEC DOES KICK IN IN NEUTRAL (provided your above the threshold temp). I don't see the problem this could cause anyone... the bike's in neutral after all... it just sits there but screams more!!

In the cases where I have gone up into VTEC RPMs with the temperature below 64ºC (the first time I just had to see what it was like and lately this may happen when I'm in a hurry and forget to up shift before hitting 6800 RPM) it just keeps climbing in the typical, docile, non-VTEC fashion... no kick-in-the-pants VTEC engagement and obviously, relatively less power than if VTEC were operational... but it keeps climbing, freely, not like in your case... so I'm real sorry to say it but, something is possibly wrong with your bike... still... or again... :angry:

In the end, it doesn't matter so much if the sensor's for the VTEC are reading the coolant or the oil temp... they are programmed to act at a certain temp, which one supposes Honda has made sure is high enough for oil pressure to be sufficient for VTEC operation.

[image: View Post]Bent, on 01 April 2010 - 07:15 PM, said:

The M3 I used to own had a factory and accurate oil temp. gauge and I put one on the Harley I used to have (I admit it, I'm so sorry.... :rolleyes: ).


Did the Harley oil temp gauge have an external probe to gauge the temperature of the oil it dripped on the ground?

[image: View Post]Tightwad, on 01 April 2010 - 05:41 PM, said:

My thought was the wax idle unit�did I possibly tweak something in my recent engine work? How can I check for correct functionality?


Dunno bout that Josh... the wax idle unit only affects the RPMs the bike idles at... can't see how it would affect things at 8000 RPM...

R u getting really low fuel economy??

Ok...I will try to answer all without multi-quotes...forgive me.

Yes, this is post valve check, then post cam chain breaking, then post head replacement....lots of posts.

I have terrible fuel economy...probably from not riding it at all, just running it in the garage...can't speak to actual moving fuel economy yet.

I sat and watched the wax idle unit work yesterday, more interesting than watching paint dry, but less than watching golf. The wax idle on my bike doesn't raise the RPM at all, but it does extend when the unit warms up...thus it is working just fine but not adjusted to raise the idle (no problem in TX really).

Do I need to go to 8K RPM? Not really, but I don't recall it having the inability to previously, so the question of being off a tooth somewhere was a concern...the fact that the restriction is only before 150 degrees (estimated, not 100% exact) makes me really wonder. Given the spotty history my bike and I now share, I am hesitant to put it back together before I know all is ship shape...but I want to ride!

The last issue is one of engine noise...I have become terribly leery of any noise. I hear a noise now (may just be me!) that I probed for with the stethoscope (buy one, they are great!). Oddly enough, the clattering (very soft, can't hear it hardly at all without the scope) is loudest when touching the fuel rails. Now this is odd because I would assume engine noise would be louder touching the head, the CCT, etc...but both CCT and both heads sound the same...muted clatter...but when I touch the fuel rail it is pronounced.

You've come so far with this TW. :fing02:
Although you live in Texas (USA), and not in Texas (Qld, Oz) my concern would be the cold start idle not happening.

At 150deg I'm pretty sure >8,000 rpm should be attainable... but for me it takes a ballet with the throttle and starter valve lever (manual).
That's on the street... I might forget to back it off a bit from startup, and if the need for extended revs arise, I'll start closing the lever whilst opening the throttle.
Can't say it feels like a limiter, or over fueling or whatever, I just realise this is what she likes... if the need arises.

Maybe a starter valve sync (dunno if ya already tried). You could just be at the mercy of the wax unit and PGMFI.

Good to hear she's up and running though.
Pretty sure you nailed the timing.

Prior to putting it all the way back together...anyone have ideas/input on the noise that is loudest on the fuel rail?

[image: View Post]Serenity_VFR, on 02 April 2010 - 10:02 AM, said:

[image: View Post]Bent, on 01 April 2010 - 07:15 PM, said:

The M3 I used to own had a factory and accurate oil temp. gauge and I put one on the Harley I used to have (I admit it, I'm so sorry.... :rolleyes: ).


Did the Harley oil temp gauge have an external probe to gauge the temperature of the oil it dripped on the ground?


It never leaked a drop but it was a POS compared to the BMW's and Hondas I've owned. Just the facts... :warranty:

Is the noise noticeable without the stethoscope?

[image: View Post]Tightwad, on 02 April 2010 - 10:28 PM, said:

Prior to putting it all the way back together...anyone have ideas/input on the noise that is loudest on the fuel rail?


Your injectors make a lot of noise in the fuel rail - the solenoids can be quite noisy and indeed on quiet engines which are idling you can often hear the injectors, as they are the noisiest part of the engine.

As for your problem, your engine should rev above 8,000rpm regardless of how cold it is. I know mine will happily rev out when it's cold, although without VTEC engaging it runs out of puff.

[image: View Post]Vee-Ef-Ar, on 02 April 2010 - 05:26 PM, said:

You've come so far with this TW. :fing02:
Although you live in Texas (USA), and not in Texas (Qld, Oz) my concern would be the cold start idle not happening.

At 150deg I'm pretty sure >8,000 rpm should be attainable... but for me it takes a ballet with the throttle and starter valve lever (manual).
That's on the street... I might forget to back it off a bit from startup, and if the need for extended revs arise, I'll start closing the lever whilst opening the throttle.
Can't say it feels like a limiter, or over fueling or whatever, I just realise this is what she likes... if the need arises.

Maybe a starter valve sync (dunno if ya already tried). You could just be at the mercy of the wax unit and PGMFI.

Good to hear she's up and running though.
Pretty sure you nailed the timing.



1998 5th gen... manual choke... forget to back it off = running overly rich... once your bike is warmed up, choke off dude!!

From what I can gather Josh, you're saying that ambient temp is not low enough for your wax unit to raise the RPM at start-up idle... so I don't see the wax unit being the problem... if, on the other hand, the idle revs weren't dropping once warm, then the bike could run sluggish at ALL revs due to too rich a mixture, that would be wax unit failure, but your case is the opposite, it loses power when cold still... and yet you say it's not idling higher at start-up... even though the wax unit appears to be going through the motions (extending??)...

I would tend to forget the noise if you need the stethoscope to really hear it.

Are you sure it won't rev higher or just takes longer and seems sluggish (because compared to when VTEC kicks in, it does seems relatively sluggish, although it definitely does climb in revs without too much trouble, just not with the same gusto).

I might be able to feather it past the 8500 mark, but it most definitely stops there if I just use WOT. I am going to run with it as it is and keep and eye on things.