Engine problem - What to try next? - Page 5 - CBR Forum - Enthusiast forums for Honda CBR Owners

CBR 900RR 1993 - 1999 Honda CBR 900RR

Engine problem - What to try next?

  #41  
Old 03-16-2019, 12:04 AM
Member
Thread Starter
Join Date: Dec 2018
Posts: 43
Default

Originally Posted by 74demon View Post
Most floats are adjusted by bending a tab so the needle shuts off the fuel when they get to a certain level. Floats can also go bad and leak internally causing them to not float and the fuel never gets shut off.
Fortunately, or unfortunately, the floats are one piece plastic. The needle valve just slides in between two plastic tabs, so there's nothing to bend. They are translucent, so it would be easy to see if fuel was leaking into them. I can't imagine how they could get out of adjustment being one solid plastic piece, unless it was broken or heat damaged (distorted). Manual says if the float height is out of spec (I just measured these, and they are in spec), they must be replaced.

Thank you for the info!
 

Last edited by MM900RR; 03-16-2019 at 12:15 AM.
  #42  
Old 03-16-2019, 12:23 AM
CaBaRet's Avatar
Super Moderator
Join Date: Oct 2016
Location: UK
Posts: 1,700
Default

Just let it dry out , take the pump electrical connections off the pump ,take plugs out spin the engine to try and blow anything out ,once you think its clear, connect the auxiliary petrol tank ,plugs back in and see if it will fire, easier to control flow from the auxiliary tank
 
  #43  
Old 03-16-2019, 12:38 AM
Member
Thread Starter
Join Date: Dec 2018
Posts: 43
Default

It's just so puzzling how fuel could flow from the tank, through the filter, pump, and carbs, and fill up the intake tract (guessing close to 1/2 liter or more per cylinder).... just sitting, key off. And it was all carbs (well, 1, 3 & 4... guessing #2 as well, but couldn't tell since intake valves were open.) I'm really being taught a lesson to not let my bike sit for 15 years aren't I?
 
  #44  
Old 03-16-2019, 12:50 AM
CaBaRet's Avatar
Super Moderator
Join Date: Oct 2016
Location: UK
Posts: 1,700
Default

One thing now is you know your getting too much fuel at the carbs, if floats ,jets and pilots screws are correct , we have to look at outside forces , that leaves the pump, is it a new one or existing, if the pump is running all the time it will force more into the bowls ,in the same case if its letting fuel pass then its faulty, try the method in #42 just to see
 
  #45  
Old 03-16-2019, 12:56 AM
Member
Thread Starter
Join Date: Dec 2018
Posts: 43
Default

Perhaps the original needle valves are sticky from being aged, allowing only a slowing filling bowl (maybe even starving the needle jet when throttle is opened, hence little to no response), and now they are stuck open.

I'll replace them with new tomorrow... see what happens.
 

Last edited by MM900RR; 03-16-2019 at 02:31 AM.
  #46  
Old 03-16-2019, 01:08 AM
Member
Thread Starter
Join Date: Dec 2018
Posts: 43
Default

Originally Posted by CaBaRet View Post
One thing now is you know your getting too much fuel at the carbs, if floats ,jets and pilots screws are correct , we have to look at outside forces , that leaves the pump, is it a new one or existing, if the pump is running all the time it will force more into the bowls ,in the same case if its letting fuel pass then its faulty, try the method in #42 just to see
I definitely agree with your reasoning. The only reason I haven't suspected the pump is, I could tell when it was and wasn't pumping (and it seemed correct). This pump is unlike one's I'm familiar with. It pulses (rather than having a continuous flow impeller). When it operates, you can feel it 'tick' every once in a while (most of the time, it does nothing). With the aux tank, I see the fuel line 'jump', every time it pulses (which is once every 2 or 3 seconds when engine is at idle). I'm sure the pulses speed up with higher fuel demand. At first, I didn't think it was working, but I did a flow rate test as per service manual and it passed.

But I think you're correct... it should not allow fuel to pass through it when it's not pumping (or not powered.) I was going to replace it just for good measure (regardless if it seemed to be working), but those OEM pumps are expensive! Nevertheless, I'm running out of things to blame...so pump is next.

 
  #47  
Old 03-16-2019, 01:09 AM
CaBaRet's Avatar
Super Moderator
Join Date: Oct 2016
Location: UK
Posts: 1,700
Default

Seems a plan , but just in case use the Aux petrol tank without the pump when you do start for the first time, gravity feed will work
 
  #48  
Old 03-16-2019, 01:17 AM
CaBaRet's Avatar
Super Moderator
Join Date: Oct 2016
Location: UK
Posts: 1,700
Default

If the pump is running like you say then thats how it should work, but doesn't explain the fuel at the inlet, think your onto the right cause with the bowl's and float needles
 
  #49  
Old 03-16-2019, 01:28 AM
Member
Thread Starter
Join Date: Dec 2018
Posts: 43
Default

I really hope so. I'm ready for the Eureka moment... and smelling like something other than petrol.
 
  #50  
Old 03-16-2019, 02:25 AM
Member
Thread Starter
Join Date: Dec 2018
Posts: 43
Default

Just reread my 'theory' regarding possibly stuck float needles... that made no sense. (Note to self, don't post late at night.) I was confusing float needle and jet needle. If the float needle was stuck closed.. float bowl would be empty. No fuel for anything. Only way to get fuel through just the idle circuit (that I can think of late at night), is if main jet was clogged...which it definitely isn't. So scratch that theory. (Although stuck open could explain the flood of fuel in the intake.) Editing that post so I sound a bit less ignorant.
 

Last edited by MM900RR; 03-16-2019 at 02:32 AM.

Thread Tools
Search this Thread
Quick Reply: Engine problem - What to try next?


Advertising
Featured Sponsors
Vendor Directory

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.