Rubbish rubber

[frodef]

For (quite) a while now, whenever I poked my fuel lines a little bit, gasoline would be happily squirting out from massive cracks. Also, there seemed to be a crack in at least one throttlebody rubber boot. And I needed to remove the tank for various other reasons too, so it was finally time for a rubber upgrade.

Pulling off the tank was easier than I thought, really, following Haynes' instructions. Then getting the whole throttlebody assembly off was also quite reasonable, even without taking off the fuel rail and injectors like Haynes insisted.

There must have been a bucketfull of grime and pebbles behind there, btw.



I'm changing those boots and all the fuel lines. And the fuel filter, air filter, front brake switch, and perhaps fix a hole in the tank right under the pump.

[jacksdad1963]

Make sure you use the correct grade of fuel hose, as it must be ethanol-proof!
As I'm going to change all my lines soon, including the ones inside the tank, I'll use 'submersible' grade ethanol-proof hose for all lines, 2 metres will be plenty  :2thumbup:
Cohline fuel hose is a good one: do we need 8mm I/D?
Did you say you have a hole in the fuel tank?

[frodef]

I suspect there's a tiny hole there, although it could be oil or something squirting from somewhere else... perhaps gasoline from the rotten fuellines? It's on the left side seam, and the paint is coming off there. It looks like it's been dripping onto the cylinder head cover, but the marks there are looking oily-orange, so I'm not really sure what's going on (as usual).

[rbm]

A hole in the left side seam around the fuel pump area is typical.  Water collects in that area because of the design.

Submersible grade fuel lines (SAE 30R10) are only mandated for use inside the tank and can be used optionally outside the tank.  Such hose is costly and most use SAE 30R8 fuel injection hoses outside the tank. Useful information: http://www.motobrick.com/index.php?topic=1042.0

[frodef]

Useful information: http://www.motobrick.com/index.php?topic=1042.0

I did pretty much exaclty this on my K75, except I didn't remove the lower air box (which as he notes is bolted on), I found if I just pulled at the airbox a bit, I'd get the fuel pressure regulator just past it.

[jacksdad1963]

The Cohline submersible fuel line is about £10 per metre from Merlin Motorsport (I think it was them anyway!) so around the same price as other stuff: I'm going to buy 2 metre of it rather than mess around getting a metre of each type and then running short....or more likely for me, fitting them wrong way round!  :hehehe
My fuel tank went in just the same spot: when fitting a heat blanket I noticed a blemish in the paint, picked at it....and went straight thru the tank! Lucky lucky me....soon fixed with a 1 oz pack of Permatex Gas Tank & Radiator Repair, £8.00 with free delivery int UK found on ebay, half price  :2thumbup: Can't even see the repair if you're careful so no paint repair needed

[frodef]

A hole in the left side seam around the fuel pump area is typical.  Water collects in that area because of the design.

It turned out there was a neat little 4 mm hole there that was stuffed with some sort of putty by some PO.



I'm trying to close it with aluminum brazing. My first attempt looked reasonable to me, but alas it leaked quite a bit. I'll try once more later today with better prepping.

[frodef]

It seems my brazing skills are about equal to my welding skills, so practice makes slightly less rubbish. On my fifth or so attempt I was finally able to make the hole at least somewhat leakproof. I'll have a final check tomorrow if it's damp or not, but it was looking promising. For anyone else trying to braze up a tank, you'll probably want to use some appropriate flux.. I used some regular soldering flux, and it seemed to at least help out somewhat. Now I just need to get hold of some mystic red paint to gloss over my handiwork.

Anyhow, after I figured out I should give the K some fuel for the effort, the thing started up and seemed reasonably happy with its new rubber bits. Idling wasn't so good (it stalled after a while), but I'm hoping that's due to the now absence of false air, and is fixed with a TB tuneup.

I struggled a bit to reseat the fuel pump inside the tank when I reassembled it, and on my test-drive there seemed to be some strange ticking or rattling noises from it... any typical pitfalls there?

[jacksdad1963]

Good job there  :2thumbup:
The fuel pump is noisy when there's not much fuel in the tank, so that may be a simple reason for the noise
Before I fixed my fuel gauge I would ride using the mileage for guidance, but a surefire warning was the fuel pump whining when it got low on fuel: I've heard many riders use this noise as a re-fuel signal!

[frodef]

Well I tried to "tune" the TB today by more or less blindly turning the brass screws. I only managed to make it worse, so now it won't idle almost at all, and there's quite a bit more backfiring when "idling" at speed. Guess I'll have to hook up those bottles and do the balancing right. Or if that fails, find someone with a clue and a carbtune.

[rbm]

Some pumps whine and sound like a swarm of bees.  But the sound is not reminiscent of ticking or rattling.  The pump surround has two clips that engage slots on the plate inside the tank.  They have to be seated correctly to secure the pump.  They are also polarized so it is only possible to insert the pump one way.  The surround will not seat properly if it is reversed.

The only other thing I can think of that might cause the sound is the fuel filter hitting a part of the tank.  Is there a hose inside your tank coming from just under the fuel filler cap and connected to the gauze filter on the fuel pump?  That hose tends to harden up, and break which might cause a rattling sound.

[rbm]

Well I tried to "tune" the TB today by more or less blindly turning the brass screws. I only managed to make it worse, so now it won't idle almost at all, and there's quite a bit more backfiring when "idling" at speed. Guess I'll have to hook up those bottles and do the balancing right. Or if that fails, find someone with a clue and a carbtune.

It might be very difficult to return the brass screws to their former positions if you failed to count the number of turns they were set at before you fiddled with them.  On a normal setup, the brass screws should be approximately 1.5 turns out from a seated position.  Try to regain that standard setup by turning each screw clockwise until gently seated and then anti-clockwise 1.5 turns.  See if the motor responds.

[frodef]

It might be very difficult to return the brass screws to their former positions if you failed to count the number of turns they were set at before you fiddled with them.  On a normal setup, the brass screws should be approximately 1.5 turns out from a seated position.  Try to regain that standard setup by turning each screw clockwise until gently seated and then anti-clockwise 1.5 turns.  See if the motor responds.

I failed to count them, of course. I did try to reset to 1.5 turns, but it didn't seem to help. I haven't had the time yet to look at it closer, but I'm starting to suspect I did something wrong with the TPS. I don't know how that thing works really, but when I googled my symptoms it seemed to match how someone described it to operate.

BTW I was thinking about a homemade vacuum comparator/TB syncer, and it occurred to me that the simplest design would be simply three long tubes (2 meters or so) going from each cylinder and into the same bottle of colored fluid, with the "long" part being laid out along a vertical board (1 meter?). This way, there's no "complicated" nipples/connectors, and when all is said and done the fluid automatically runs back into its container, so there's no mess during storage... Am I overlooking something?

[frodef]

but I'm starting to suspect I did something wrong with the TPS. I don't know how that thing works really, but when I googled my symptoms it seemed to match how someone described it to operate.

Here's the thread about the TPS: http://www.motobrick.com/index.php?topic=1522.0

...and during the recent 10-minute rain pause I was able to verify that the TPS switch in fact didn't close at zero throttle or otherwise. So there's my (first) idling problem I suppose.

[frodef]

...and during the recent 10-minute rain pause I was able to verify that the TPS switch in fact didn't close at zero throttle or otherwise. So there's my (first) idling problem I suppose.

...turned out the issue was that I'd left the "choke" on and that's why the TPS didn't close. With the "choke" off, the TPS operated just fine. Sigh.

[frodef]

Picking up this thread, it turned out the issue was a massive air intake leak because I'd forgotten to use sealant between the engine block and the rubber pieces. Idling is much better now, so all in all I think the whole operation was a success (eventually)  :euro

[frodef]

Rode some 1200 km this weekend (my butt isn't quite ironized yet), and the engine runs wonderfully at speed, idling, and everywhere inbetween. The mended tank hole seems to hold up fine (just looks ugly and needs refinishing), and all in all I'm once again amazed at how well this almost 30 years old thing runs.    Seems I'll be taking the bike across europe in a few weeks, for the (pen-) ultimate endurance test.