Honda Motorcycles - FireBlades.org banner

81 - 100 of 121 Posts

·
Registered
Joined
·
1,063 Posts
Sorry for the delay, finally got a bit of time back on it again today and yesterday. I fitted a set of OEM coils and leads because they were changed not long ago, no difference.

Got a complete set of carbs off a running bike - exactly the same problem! As soon as I give any throttle at all it dies. I've just checked the static timing again and it looks perfect so I'm going for another rectifier and then thinking ECU or loom. I am going to look at fuel pump again because I noticed the diaphragm of the original pump is leaking now too
Please forgive my mechanical ignorance but I have not heard of a carbureted bike with an ECU or fuel pump. Is this so???
 

·
Registered
Joined
·
171 Posts
Discussion Starter #83
Yep perfectly common to have both, the fuel pump is only low pressure for the carbs

As for breather pipes, none were moved on the original and the new ones came with them fitted so no changes there. any thoughts are more than welcomed though!!!
 

·
Registered
Joined
·
6 Posts
It sounds like the fuel supply. That would mean the inlet screen from the fuel tap, the pump or the fuel lines. You could try rigging up a fuel supply that gravity feeds into the carbs, thus bypassing fuel pump and inlet screen. I don't know how practical that might be to test under load but you get the idea.
 

·
President: Team Full Chat
Joined
·
7,352 Posts
Please forgive my mechanical ignorance but I have not heard of a carbureted bike with an ECU or fuel pump. Is this so???
ECU is aka CDI or even ECM. All the same, whichever you want to call it, it controls ignition. Later ones with FI then control ignition and fuel.

The 92-95 900's all had fuel pumps, as only a helper, and did not build pressure like an FI bike.
 

·
President: Team Full Chat
Joined
·
7,352 Posts
:( Oh man I'm running out of ideas

I took it out for a spin, ran perfectly for the first 5 minutes. Started to warm up so I gave it a few revs and spluttered a bit then cleared itself and ran well. It was revving freely to about 7-8k rpm no problem.

Then it died again. Any kind of throttle and the engine gave up completely. I managed to limp home with the idle adjuster turned up so it was at about 3k rpm and the choke out to give a bit of fuel, not a pleasant journey at all.

It was popping and banging in the exhaust if I put the clutch in but all the plugs look slightly lean if anything. I put the CO meter on it and it's all over the shop, one minute rich and the other lean.

I'm toying with the idea of a second hand set of carbs to change everything in one go
Compression test yet?

One minute it sounds fuel, the next it sounds like weak ignition, then the next it sounds like BOTH.

If you swap carbs and it still does it you have a different problem (obviously). I don't think it's a fuel problem now, your carbs have been well gone through.
 

·
Registered
Joined
·
171 Posts
Discussion Starter #90
I agree with you Ian, unless the second fuel pump I tried was faulty (although new). I've ordered a third to be sure!

I have a set of plugs on their way (even though these are pretty new) and I have replaced the rectifier and very burnt out connector to no avail.

I haven't done a compression test for a little while, it was fine last time but I'll give it a whirl in the next few days
 

·
Registered
Joined
·
171 Posts
Discussion Starter #91
New fuel pump + lines from a clean can of fuel - still bad. Let it idle for a couple of minutes but any throttle and it died.

Changed the plugs for new again, still failed.

Went to take a video to show you guys before setting fire to it - all better! Watch it clear in the new video and I have attached an old one showing it about to die with throttle, also getting the most I can out the idle adjuster and about to stall on choke.

I'm wondering if it is fuel and it took longer than I thought to empty the float bowls?
 

Attachments

·
President: Team Full Chat
Joined
·
7,352 Posts
New fuel pump + lines from a clean can of fuel - still bad. Let it idle for a couple of minutes but any throttle and it died.

Changed the plugs for new again, still failed.

Went to take a video to show you guys before setting fire to it - all better! Watch it clear in the new video and I have attached an old one showing it about to die with throttle, also getting the most I can out the idle adjuster and about to stall on choke.

I'm wondering if it is fuel and it took longer than I thought to empty the float bowls?
Is that green can the fuel tank? If so, just for shits and giggles, use a remote tank without the fuel pump and hang it from eye level. We've been working on this so long I can't remember if we've done this. Even on the original bike, the fuel pump is under the fuel tank, and not trying to move fuel against gravity. It actually uses gravity as an assist.

Maybe the bowl level is getting messed up, too much or not filling enough.

This is such an odd issue.
 

·
Registered
Joined
·
171 Posts
Discussion Starter #93
Yep that's the fuel and working perfectly still. It's certainly an odd issue. I'm going to try using the old tank to prove positive the issue then it's a full tank drain and endoscope!
 

·
Registered
Joined
·
276 Posts
Could be on to something there. A bit of the old 'thinking outside the square'.:wink
Ian's comment :thumb::

"Maybe the bowl level is getting messed up, too much or not filling enough."

...... caused the idea to float up to a strange height within my subconscious bowl ..... :grin
 

·
Registered
Joined
·
171 Posts
Discussion Starter #98
I'm afraid I can't compare to a bike because I've only had the car but if it was angle then it should have been there for the last 2-3k miles which have been perfect

I drained the tank as much as I could with a syphon pump and then pumped out the rest through the lines. The lower I got the whiter it was so there was definitely some water in fuel going on. I need to crawl under and try and get some more out (there's about half an inch of fuel left in) but I think this was a contributing factor. The endoscope didn't yield any obvious issues though
 

·
Registered
Joined
·
276 Posts
Could be on to something there. A bit of the old 'thinking outside the square'.:wink
I'm afraid I can't compare to a bike because I've only had the car but if it was angle then it should have been there for the last 2-3k miles which have been perfect
Ah, I understand. Just for interest, in the bike, the bottom of the sump is horizontal as is the crankcase split-line (crankshaft and clutch centres are on this line and horizontal).
 
81 - 100 of 121 Posts
Top