1993 CBR900RR - rebuilding an iconic super sport

I remember putting many miles on my 900rr, even once riding to the Dragons Tail. The seat is a piece of brick and I replaced it with a proper Corbin, which is dished out to better fit me. I recommend the same if you plan on riding a lot. Otherwise, buy a bottle of Monkeys Butt for the thigh chafing!!!

eyhonda said:

I remember putting many miles on my 900rr, even once riding to the Dragons Tail. The seat is a piece of brick and I replaced it with a proper Corbin, which is dished out to better fit me. I recommend the same if you plan on riding a lot. Otherwise, buy a bottle of Monkeys Butt for the thigh chafing!!!

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And a cup, because this thing is about as friendly to the wedding tackle as my Monster was - ouch

Worst cb650 ever said:

And a cup, because this thing is about as friendly to the wedding tackle as my Monster was - ouch

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;D ;D ;D ;D ;D 8) 8) 8) 8)

So apparently the bike gods are punishing me again for some unknown infraction...

I decided to go to the local bike night last night, as it might be the last one of the year. As the 650 is a big question mark, and the 360's carbs are about 900 miles away from me now getting some love (thanks PJ! ) I was left with the 900.

Which wouldn't start. I just rode the damn thing, wtf?

After some poking, I discovered that the fuel pump was not running. I took the cover off the back of it and found points. Points!?!?!? In 1993!??!!? Badly burnt points to be specific. The bike has a diaphragm style fuel pump, similar to those installed on little British cars.



I cleaned up the points with a points file (oh the tools I have collected), and hooked it up to power again. It worked, but man those points were sparking. Yes, let me install the spark generator under the fuel tank and fill it with gasoline

Some Googling revealed that many folks just remove the fuel pump when it fails, and use gravity feed for fueling the carbs, so I decided to try that. I hooked the line from the fuel filter to the tank and then directly to the carbs and removed the fuel pump control relay. A couple seconds of cranking, and voila, the bike fired up! I geared up and headed out for a test run.

About 10 seconds after I gave the bike some throttle, it sputtered to a stop and I couldn't restart it. On a major 5 lane road. In the dark. Shit.

I pushed the bike into a Denny's parking lot (I'm sure stranger things have happened in that parking lot), and after some poking, still couldn't get it to fire. Built not bought, eh Rich? ;D

Some thinking through the DTT "what the shit is wrong with my junk?" checklist brought me to "plugged fuel tank vent," so I popped the cap on the tank. Hiissssssss. Huh, that's not good. But, breaking the vacuum was enough to get the bike started and running ok enough on choke to get me home.

After waking away from the bike for a little bit, I pulled the fuel tank again to inspect the vent and overflow tubes detailed in my factory service manual. There was no overflow tube, because it's much more exciting to let overflow gas go right onto a hot engine, and the vent tube was plugged with a small bolt. Previous owners man, previous owners. I pulled the vent tube to remove the bolt and the tank made another audible hisssssss as air flowed into the tank. I think I may have found the issue. I put the bike back together and put it on the charger, as it was too late for a ride on a bike with a Kerker pipe.

Some more research this morning led to me discovering that repair points kits are available for the fuel pump. Here's the repair walkthrough:

http://cbrforum.com/forum/stickies-91/how-repair-your-f3-fuel-pump-102151/

And here's the part:

http://davidsilverspares.com/CBR900RRP-FIREBLADE-1993/part_141068/

I still want to see if the pump is really needed, but I'll probably repair it and reinstall it for easier starting.

I tell ya, these damn bikes...if I wanted electrical problems, I would have bought another Italian bike!

Ha ha ha...But you rode it home. That's an interesting design as to the fuel pump...gotta admit I've never had one apart, tho.

Rich Ard said:

Ha ha ha...But you rode it home. That's an interesting design as to the fuel pump...gotta admit I've never had one apart, tho.

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Yea, choked at 2000RPMs as touching the throttle would make it stall, and feathering the clutch in second the whole way lol

Apparently that design fuel pump is used as far back as the '80s VFRs through the late '90s superbikes. Yamaha uses the same pump as well. All are shitty.

You'll need the fuel pump to get all the fuel out of the tank. Otherwise, it will die with half a tank full of fuel......and probably no warning as to when....

Interesting that the fuel pump can be "fixed". Most are just sealed units that you throw away and then spend $200 to buy a new one. I'd say that's a good design as opposed to a bad one

hillsy said:

You'll need the fuel pump to get all the fuel out of the tank. Otherwise, it will die with half a tank full of fuel......and probably no warning as to when....

Interesting that the fuel pump can be "fixed". Most are just sealed units that you throw away and then spend $200 to buy a new one. I'd say that's a good design as opposed to a bad one

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Yea, I pulled the trigger on the pump rebuild kit because I found mixed reports about running without a pump. I think Honda changed the design of the fuel tank in '98 to allow gravity feed to be reliable. At least I know if the pump dies again I can bypass it. I do think I could use most of the fuel in the tank though, because the petcock pickup is at the lowest part of the tank. If I was running hard enough to empty the float bowls quickly (high speed high RPM), I could go lean and punch a hole in a piston. That would be Bad.

Yep - I think your biggest concern would be leaning out the bowls without a fuel pump.

The carbs sit so high up on these bikes (and almost vertical) that gravity feeding them is pretty hard.

Even though you'd probably get most of the fuel out of the tank, the last part would be coming out very slowly without a pump.

Yea, I think I'll leave the bike parked till I can rebuild the pump. At least I have the tank vacuum problem worked out.

It's a problem on more honda models.
The problem mostly occurs if the pump runs dry (a.i. gets no fuel).
The plunger inside of the pump will start to vibrate? and the contacts will heat up and eventually burn away.
The solution is to solder a diode parallel to the coil of the pump, this will prevent it from sparking.
Also; try not to run it dry.
Here's a link to a site were its explained (sorry its in Dutch, google translate? )

http://www.honda-deauville.nl/documents/Handleiding_plaatsen_diode_op_benzinepomp_Honda_NT650V.pdf

Hope this makes sense, English is not my native....

You could throw a cheap auto pump like this:

http://www.ebay.com/itm/Super-Auto-E8016SX-Low-Pressure-Electric-Fuel-Pump-/400374478141

they are solenoid pumps, solid state, no points....I used them in the past for my carbureted cars, reduced vapor lock.

They need to be soft mounted as they do pulse and if hard mounted, will be heard.

Just another possibility...

I removed my pump and gravity fed it. I had enough range out of the tank. So, it wasn't an issue for me. I leaned the bike over enough to swish the fuel around so there wasn't old fuel sitting in the bottom.

Prutsert said:

It's a problem on more honda models.
The problem mostly occurs if the pump runs dry (a.i. gets no fuel).
The plunger inside of the pump will start to vibrate? and the contacts will heat up and eventually burn away.
The solution is to solder a diode parallel to the coil of the pump, this will prevent it from sparking.
Also; try not to run it dry.
Here's a link to a site were its explained (sorry its in Dutch, google translate? )

http://www.honda-deauville.nl/documents/Handleiding_plaatsen_diode_op_benzinepomp_Honda_NT650V.pdf

Hope this makes sense, English is not my native....

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It makes perfect sense to me - thanks for the link. I actually think I have some 1N4007 diodes around somewhere. At least "diode" and schematics are the same in any language. Conveniently, I have to desolder the black pump lead to install the rebuild kit on the pump, so I'll solder in the diode at the same time. I probably should replace the fuel filter and fuel lines while I'm at it.

I love this place - someone from the other side of the world has reached out over the Internet to help. Thanks!

mydlyfkryzis said:

You could throw a cheap auto pump like this:

http://www.ebay.com/itm/Super-Auto-E8016SX-Low-Pressure-Electric-Fuel-Pump-/400374478141

they are solenoid pumps, solid state, no points....I used them in the past for my carbureted cars, reduced vapor lock.

They need to be soft mounted as they do pulse and if hard mounted, will be heard.

Just another possibility...

Click to expand...

You know, funny you mention that, as my Dad offered me a solid state pump similar to that one that he ended up not needing on his VW Beetle powered dune buggy. Gravity feed worked fine on that project too! I'm hoping that actually having an open breather hose to the tank will also reduce vapor lock. In fact, I wonder if the plugged breather line was causing damage to the pump due to induced "vapor" (actually vacuum) lock?

eyhonda said:

I removed my pump and gravity fed it. I had enough range out of the tank. So, it wasn't an issue for me. I leaned the bike over enough to swish the fuel around so there wasn't old fuel sitting in the bottom.

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Thanks, I won't be afraid to ride the bike until the pump gets here then. I'll still reinstall the pump, but it's always good to have input from someone with experience!

Also, in case someone else doesn't have diodes lying around the house, Radio Shack does:

http://www.radioshack.com/product/index.jsp?productId=2062589

This assortment should have some 1N4007 diodes in it, and $3.49 is cheaper than shipping from an online parts supplier.

Google Translate had no problem with the PDF either, and details the physics/electrical theory for why the diode prevents points sparking.

Well, I actually got a ride on the bike that didn't involve stalling, vapor lock, sparking points, or praying to make it home on choke and hutzpah. I did freeze my ass off though!

Part of the ass freezing was due to me forgetting I had pulled the instrument cluster to fix a broken mounting peg. I ended up drilling out the plastic housing where the peg was broken off and installing a bolt in place of the peg:



Since several (well, all) of the mounting bolt tabs/holes are gone, I put a nut on the bolt after it was pushed through the rubber mounting grommet.

Tada!



Rich, I'm sorry, but I replaced your favorite grip ;D



Dat ass:



The replacement plastics should be on my porch fresh from some dude in Florida, and the fuel pump rebuild kit and a hydraulic rear brake light switch are on their way as well. What's left is finding a source for replica decals, figuring out turn signals, and getting a replacement left mirror, as the glass is missing from the one I have.

My thoughts about turn signals are leaning to flush mount or mirror/turn signals in the front, and an integrated brake light/turn signal unit for the rear. One of the previous owners took a saw to the stock rear fender, removing the stock turn signal mounts, the license plate mount and lights, and some other plastic, so until I locate a rear fender that isn't hacked up my options are limited. I'm open to suggestions!

Ok, I have the plastics, and have slowly been messing with them getting them installed. I haven't done much with them, as I knew I'd need to tear into the bike to reinstall the fuel pump properly, and I was waiting for the rebuild kit.

I was getting annoyed yesterday because the fuel pump kit and the brake pads I ordered last week hadn't shown up yet, so I checked the tracking info. Delivered Saturday? I didn't see any thing delivered on Saturday! Wait, I didn't check the mailbox on Saturday…

Yea, so I have the new pump points and brake pads now ;D

Old vs. new fuel pump points:





It is a quite ingenious design, using the springiness of the rubber diaphragm to work against the point, and also gracefully stopping the pump when the fuel pressure increases because the float needles have shut. Hopefully with new points and a diode it will work great again.

I spent most of the weekend and yesterday working on the garage instead of the bikes in it, but as a result I have a working air compressor and grounded electrical outlets, as well as the ability to turn the garage attic lights on and off from the main floor. I also replaced the folding attic ladder with one that wasn't badly installed and broken, so I can actually use that space again. I set up a winch and hauled the air compressor into the attic space and wired up a dedicated switched outlet for the compressor. It gives me more floor space and makes me not have to listen to the compressor as much, which is nice

Ok, I installed the new points and the diode. I tested the pump with and without the diode, and the difference is immediately apparent. The points alone spark merrily, but with the diode installed there is no visible sparking at all. Very impressive!

However, should you hook up power to the pump backwards, perhaps because some boneheaded previous owner spliced in incorrectly colored wires, you will indeed burn up your poor little diode. Not that I'd know anything about that ;D

Materials gathered together:



First I desoldered the lead to the old points:



Then solder in the black lead to the replacement points as well as the anode lead of the diode. The cathode lead goes into the black with blue tracer wire on the pump. I removed some insulation with a knife, wrapped the diode cathode lead around the bare wire, and soldered it in place. The second time I installed a diode I remembered to put some heat shrink tubing over the diode first. I also wrapped the junction of the diode and wire with electrical tape for further insulation.



The whole mess fit neatly under the end cap of the pump, and I hope that this will be the last time this pump needs attention.