Can i modify a USA K75 to a europe version? - K-Bikes.com - Excellence in Motion
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post #1 of 12 (permalink) Old Jan 3rd, 2013, 6:45 pm Thread Starter
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Can i modify a USA K75 to a europe version?

Hello, group. Long time without posting.
I was reading about the k75 in http://en.wikipedia.org/wiki/BMW_K75

I see: "They are powered by a 740 cc liquid-cooled inline three-cylinder engine with Bosch fuel injection. The US EPA specific engine produce 68 hp (51 kW) while all others produce 75 hp (56 kW)"

I dont know why and how US models lost 7 HP.

I've a US model but i live in Uruguay, where europe model are allowed. Do you know how can i modify my bike to a european model and have a gain of 7 HP?

It sounds as a good idea for me.

Any coments are really apretiated.

Thanks all,

Fabian
K75C 1986
Uruguay
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post #2 of 12 (permalink) Old Jan 3rd, 2013, 8:40 pm
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Don't know about the K75, but had an early Canadian 85 K100RS, Eurospecs camshaft sure gave them extra HPs.

Benelli 50cc at 14
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Honda CB 750 F at 18
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post #3 of 12 (permalink) Old Jan 4th, 2013, 10:25 am Thread Starter
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Hi,
why, how it happens?
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post #4 of 12 (permalink) Old Jan 4th, 2013, 12:40 pm
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Internet Rule #1: Don't believe everything you read on Wiki.

They'd most likely change the fuel mapping in the L-Jetronic and/or the intake/exhaust cams. but I've looked at the part numbers for those in other countries like Germany and the UK and they're the same as the US part numbers. There's also no indication in the parts listings anywhere that there are different cams for different countries like there usually is..

Heck, even BMW NA doesn't have their sh*t together. If you look at the 1990 sales literature it says the K75 puts out 70 hp but the 1995 stuff says it puts out 75 hp. Weird, huh?

Is Wiki right or wrong? Got me.

I'd be inclined to just not worry about it and go riding.
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post #5 of 12 (permalink) Old Jan 4th, 2013, 2:04 pm Thread Starter
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Hi flyingduck!

i agree with you about internet, because that i've looking at the haynes manual in Chapter 2 :Engine.

it seems to have a difference in compression ratio in late US models (10,5:1) and uk ones (11:1), so they talk about 70 and 15 HP respectively.


And in chapter 7 ignition:

Advance rage:
US: 26 degrees
UK: 24 degrees

Static ignition timing:

US: 4 degrees BTDC (cranckshaft angle), 0.10 mm BTDC piston position
UK: 6 degrees BTDC (cranckshaft angle), 024 mm BTDC piston position

These are the only differences i can find.

As you say, i just need to ride!.

And as i've read, my bike is from january 86, and the gap between US and IK started " somewere between february and july", so maybe i've this 7h working.

Thanks!

Fabian
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post #6 of 12 (permalink) Old Jan 4th, 2013, 6:06 pm
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Good info. Since you mentioned the compression ratio I went to take a look at the pistons. I can't tell what the details are from the parts catalog but it does show that some sort of change over that occured to USA pistons in 6/88.

FYI: The heads appear to be the same.

I think that was also when they changed to the newer rings that let less oil seep by when parked on the side stand.

Did the change in the pistons change the compression? Got me.

Here's a post where Don Eilenberger ran dynos of an 87 vs. a 92 and got identical results:

http://www.bmwmoa.org/forum/showthre...mp-Compression


I have the 88 and 93 Haynes manual which both show the difference between the US and UK models. I'd assume they were working with an 86 or 87 when putting the 88 manual together.

One thing I did that seems (according to my not-so-reliable butt dyno) to have improved performance on my K75 was to install some Gen 2 Bosch fuel injectors that some guy was selling on Fleabay. The Gen 2s have a four hole pintel cap that atomizes the fuel better compared to the Gen 1 that shoot a single stream of fuel. The theory is that it improves combustion.

It's a popular mod among the Jeep crowd:
http://www.youtube.com/watch?v=bHf-6ohkgbA

The guy isn't selling those injectors on Fleabay anymore but if you want his email then drop me a PM.

Then there's the advancing the timing 3 degrees trick. I've neveer played with that but was thinking about trying it on my K75 later this month,

Last edited by FlyingDuck; Jan 4th, 2013 at 6:23 pm.
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post #7 of 12 (permalink) Old Jan 5th, 2013, 7:28 am
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Quote:
Originally Posted by FlyingDuck
One thing I did that seems (according to my not-so-reliable butt dyno) to have improved performance on my K75 was to install some Gen 2 Bosch fuel injectors that some guy was selling on Fleabay. The Gen 2s have a four hole pintel cap that atomizes the fuel better compared to the Gen 1 that shoot a single stream of fuel. The theory is that it improves combustion.

It's a popular mod among the Jeep crowd:
http://www.youtube.com/watch?v=bHf-6ohkgbA

The guy isn't selling those injectors on Fleabay anymore but if you want his email then drop me a PM.
Neat video, thanks for sharing.
Do you know the part number for the Bosch Gen 2 injectors that will work with a K75? I've considered getting mine cleaned but it may be better to get "new and improved".

Thanks.

Nick
1993 K75S
1991 R100RT
1982 Yamaha XJ650RJ Seca
1978 R100S
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post #8 of 12 (permalink) Old Jan 5th, 2013, 10:57 am
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Quote:
Originally Posted by stokester
Neat video, thanks for sharing.
Do you know the part number for the Bosch Gen 2 injectors that will work with a K75? I've considered getting mine cleaned but it may be better to get "new and improved".

Thanks.
Don't know the part number for them but Fleabay seller Osidetiger (not affiliated) was selling them for $25 each which is only a little bit more than getting them reconditioned. I'd guess that if you drop him an eBay message that he can hook you up.
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post #9 of 12 (permalink) Old Jan 5th, 2013, 5:51 pm Thread Starter
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Txs flying duck.

Nice video, and article.
I;m interested in the inyectors too.

As i supose now after reading, my january 86 bike has full power.

Whay i;m going to do im the future, after adjusting the valves, replace filters and may be new inyestord is to put it on a dyno for test.
If i do taht for shure i;ll post results.
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post #10 of 12 (permalink) Old Jan 5th, 2013, 8:52 pm Thread Starter
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I've just see that Gen3 exist.

http://www.youtube.com/watch?v=VfynoxL2RZI

Even a little more sprayed.
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