K75C from Kyushu to Tokyo

[gkanai]

Had time to look inside the tank for the first time. It was... not good, but not terrible. I'll be replacing the fuel level float, as that has clearly deteriorated. I'm also going to replace the entire fuel pump system just to be sure that it is new. I'm also going to treat the tank with a gas tank corrosion treatment. I'll also replace the fuel cap gaskets, etc. Photos in the next post.

There are a few different lengths of choke cable for the K75- how do we know which one to get? Take off what I have and measure?

[gkanai]

[Laitch]

A few prolonged soaks then rinses with white vinegar should help clean up the tank a little more. There is no visible vibration damper surrounding the pump and the pump is too low in its bracket. When you remove it, please post a photo of the mount and the pump separated. You're on the right track replacing that cobbled-together mess with entirely new components. One of the pump's wires looks like it could be replaced, too.

[gkanai]

A few prolonged soaks then rinses with white vinegar should help clean up the tank a little more.

Thank you. I do have some white vinegar to clean up the tank.

Will replace everything I can inside the tank.

[gkanai]

My fuel rail looks pretty bad. Do I need to consider replacing it or can I take it apart and sand down the rust and re-paint it?

Should I be replacing my fuel injectors or can I have my OEM ones refurbished somehow?

[frankenduck]

You can get the FIs refurb'd. That's what I always do.  In the US I use this guy https://www.mrinjector.us   He charges $18 each.

Look around in Japan. The prices for FI service vary quite a bit.

It doesn't look like the fuel rail is still available from BMW (13531460607) so sand and repaint is the way to go unless you can find a good one on Ebay for a reasonable price.  Getting it media blasted might be easier than sanding.

[The Mighty Gryphon]

The only critical part of the fuel rail is where the injector o-rings seal against fuel leakage.  As long as that sealing surface is good, the rail can be salvaged. 

Throw it into a pan of white vinegar for a couple days, then go over the outside surfaces with a wire brush and blow out the interior with compressed air,  follow up with a rust converter primer and paint with a semi gloss engine enamel.

[gkanai]

You can get the FIs refurb'd. That's what I always do.

Look around in Japan. The prices for FI service vary quite a bit.

Gotcha- thank you.

[gkanai]

The only critical part of the fuel rail is where the injector o-rings seal against fuel leakage.  As long as that sealing surface is good, the rail can be salvaged. 

Understood- will refurbish. Thank you!

[Gabriel70]

Hi.

Just a few ideas.
-avoid painting the engine cases. I don’t think they were ever painted. I cleaned the final drive, gearbox and engine cases with a nylon brush and wd40. The front of the engine requires a more gentle approach. Please don’t use a wire brush or nylon brush on the front engine cover.
They look great, and no signs of deterioration eight years later.
-consumables such as filters, cables etc are available from Motobins and BMW Motorworks.
-buy a can of electrical contact cleaner and clean ALL connectors including the earth point under the fuel tank.
-perhaps replace the air inlet cover. It’s cheap and makes the bike look nice.
-keep it simple. Once you start messing with paints, it can turn into a mess. I have yet to see a painted engine case which I would consider looks amazingly good. Try wd40 and a nylon brush on the end of a drill and you might be pleasantly surprised by how good it looks.
-use clean rags and cotton tips/buds.

Good luck.
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[gkanai]

Hi.

Just a few ideas.

Thank you so much for the good advice! I'm ordering nylon brushes now and will go to work.

Agreed on the contact cleaner- I'm going to have some work done by a local vintage BMW shop as well.

[Gabriel70]

Hi

Try the nylon brush, attach it to any drill, start at a slow speed until you get a feel for the brush. Apply a small amount of wd40 and use a clean rag to wipe the cases as you go.
I’m not certain how effective this technique will be for your cases"
I used the nylon brush on the final drive, the drive shaft cover and the engine side covers. The front engine covers (which covers the timing chain) I found scratches easily.
A toothbrush and wd40 is also useful for cleaning the tight spots.
Try and avoid metal brushes and chemicals.
Good luck

[Gabriel70]

Hi

I forgot to mention, all of my components were removed from the bike when I cleaned them.
Makes the job much easier.
I have attached a few photos of my k100 which has been kept in a shed for the last two years and is covered in dust.

The metal spacers on the footrests were purchased from BMW and rusted within weeks?
The wheels are not great.
I will be fixing a few issues within the next few months.

[gkanai]

I got quotes for the Wilbers and the YSS here in Japan and the Wilbers is 2X the price of the YSS. I don't think I want to pay that.

The YSS standard spring (ID46　45-60N/mm) is rated for a 45-90 kg rider I am told. I'm heavier than that (110 kgs) and YSS sells a 80 N/mm spring. Has anyone else upgraded the YSS spring to the heavier rated spring?

[Gabriel70]

Hi

A shock absorber is one of the most expensive parts on a motorcycle.
Wilbers is an expensive brand. YSS is a reasonable option.
How confident are you working on motorcycles.
Old motorcycles can have many issues and it can be expensive paying someone else to do the work.
I have a few ideas, based on my 20 years of ownership experience with a 1984 BMW K100 and a 1992 BMW K75s.
-familiarise yourself with the bike. Download the owners manual and the official BMW service manual. They can be downloaded for free.
-clean all the electrical connectors, especially the connectors under the petrol tank. Use a contact cleaner with an extended nozzle. Spray it into the open end of the connector and make certain you have a rag on the other end of the connector to catch the residue. It is not difficult to remove the petrol tank and it’s easy to disconnect all of the connectors.
-remove all of the fairings. It’s not difficult, especially your bike. It will give you easier access to your bike’s components.
-remove the rear wheel and the final drive. Once you’ve done that, check the driveshaft, in particular the splines.
The splines can be expensive to replace.
- eventually replace all fluids and filters.
-Please check that all the systems, that is, brakes, lights, fuel injection, engine, switches etc are all operational.
-a new shock absorber, which can be expensive should be one of the last purchases. No point purchasing a shock absorber if the rest of your bike is not running.
-Motobins and Motorworks BMW in the UK are a good source of cheap parts. It also depends on the currency exchange rate and postage costs.
-the official BMW dealership is where you will find the hard to get parts, especially the fasterners.

Good luck.

[The Mighty Gryphon]

Gabriel's advice is very good.  Make sure you have everything else working before making any major investments.

My personal opinion is that expensive options like a new Wilburs or Ohlins shock for our old bikes isn't terribly financially responsible.  I have had K bikes with OEM, Works Performance, Fox Twin Clicks, and YSS.  Specifically, I had two 16valve K100's, one with a Fox, and one with a YSS.  Both handled and rode the same once I got the preload and damping dialed in on the YSS.

As far as the YSS spring rate, give the YSS guys the information they ask for on how much you will be loading the bike and how you ride and go with what ever they recommend.  I know they got me a good spring, and I haven't heard of anyone else having a problem with their setups.

Finally, if you do go with the YSS, set it up with the absolute minimum preload to get as much static sag as possible.  My shock has the adjustable spring seat at the point where it touches the spring without putting any appreciable pressure on it.  I found the damping works best at the lower end of it's adjustment range.  I think mine is set about 1/4 to 1/3 of the way from minimum damping.  These settings should give you a good ride with minimum harshness and good handling in corners.

[gkanai]

Hi

A shock absorber is one of the most expensive parts on a motorcycle.
Wilbers is an expensive brand. YSS is a reasonable option.
How confident are you working on motorcycles.
Old motorcycles can have many issues and it can be expensive paying someone else to do the work.

Good luck.

Gabriel, thank you for your valuable advice. I am doing some of the work myself and having a local vintage BMW shop do some of the work as well.

[gkanai]

Finally, if you do go with the YSS, set it up with the absolute minimum preload to get as much static sag as possible.

Thank you for the guidance on the sag- that is something I did not know.

After reading so many good experiences owners have with the YSS- I agree the Wilbers doesn't make sense.

[gkanai]

So I wanted to provide an update since I haven't updated this thread.

Long story short, the K75C is finally almost fully sorted. Cosmetically it's still in the original condition but almost everything that needed to be replaced has been replaced. The last thing was the rear suspension which was the original shock and started leaking as soon as I rode it.

I found a used Ohlins online for $200 and had it sent to Ohlins Japan who told me that it's still in good working order so I had them put on a different spring for my weight. I'm hoping to have that installed soon. Without a decent rear shock, I haven't really ridden it extensively.

One thing that's come up is the injectors. I saw that European K parts specialty store had those fancy new EV 14 injectors so I bought a 3 pack. When I had them installed, it ran really rough. In googling around, I found another K75 owner who had the same experience (see video). Maybe the EV 14 injectors aren't good for the K75? I'm not sure but I'm back to the original injectors. Volimoto (the youtube video in question) is recommending the  BOSCH 0 280 155 969.

My issue with the injectors I have now is that there is quite a noticeable stumble between 2000-3000 rpms UNTIL the engine heats up. Once it heats up, the stumble gets less noticeable. I'm wondering if there's a different injector I should try or if this is common?

https://youtu.be/FrtUmF8A_M8?si=HQA54amdj7_n5RsG

[Laitch]

The original equipment one-hole injectors give superior performance and fuel economy when compared with four-hole injectors, according to many anecdotes on this forum and elsewhere. You should get your originals professionally cleaned and restored if you haven't done that already then try them in your engine.

[gkanai]

The original equipment one-hole injectors give superior performance and fuel economy when compared with four-hole injectors, according to many anecdotes on this forum and elsewhere. You should get your originals professionally cleaned and restored if you haven't done that already then try them in your engine.

Thank you- I assumed that the EV 14s were better without checking first. I wonder why that company is pushing the EV 14s when they don't work well (at least for the 2V); maybe they work on K11 or K12?

I'll look for professional cleaning of my current injectors.

[Martin]

A mates son who was an injector specialist explained why the 4 holes are a bad choice. The one hole injectors are designed to spray onto the back of the valve, this does two things it helps cool the valve and it also helps atomize the fuel mixture. A local mob cleaned my injectors with little improvement. After working out how to clean them myself I got a big noticeable improvement. A lot of the praise for the 4 hole is due to the fact they are swapping dirty one hole injectors for clean 4 hole injectors. They would have got a better result by using correct clean 1 hole injectors.  If the 4 holes are so much better why are there no Dyno comparisons? Also due to the smaller hole size 4 hole could be more prone to clogging.
Regards Martin.

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[gkanai]

Thank you Martin. I should have done more research before buying the EV 14 injectors, clearly! Lesson learned. I'll see what I can do about having my current injectors cleaned here in Tokyo.