Supertrapp Exhaust questions - K-Bikes.com - Excellence in Motion
 
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post #1 of 6 (permalink) Old Oct 22nd, 2013, 10:37 pm Thread Starter
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Location: Lisbon, (previously Colorado), Portugal
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Supertrapp Exhaust questions

ahoy mates, I just got a second K100LT, 1987 this time! I had always wanted to try stripping mine back in Portugal, but I didn't have the tools, space, resources, or impetus to do it. Plus it was all in place, looked good and did the job as requested!!

This one has already been stripped for me tho, and with a few nice extras to boot. A Supertrapp exhaust already installed, Throttlemeister cruise control bar ends, and a Progressive rear shock to name a few.

Now from the day I met 'er she has not liked to start. The cold start lever only makes it worse in fact!! If given enough time and a well charged battery she'll slowly come to life, but it requires multiple tries, and starts with the slowest, lowest, barely ticking over sort of thing that dies with the first touch of throttle. Once started, warmed up and blipped a bit everything is great, lots of power, good response, smooth power curve, no complaints. There is some backfiring as you roll off the throttle, but smooth running and fine to restart while still warm.

So, I do know the battery may be on its way out, but I don't know if there has ever been anything done to the computer to acknowledge the new exhaust. I wonder if there's any knowledge on here about steps to take to get the choke/cold start to have a positive effect, and get the old girl to leap into life like my other one (leap is a long stretch, but she started up and would idle within a few seconds, slowly getting better until I could release the cold start)

Any ideas are greatly appreciated and so happy to have a K bike again!!!


===================
/1957 BSA A10 Spitfire Scrambler
/1960 BSA A10 Super Rocket (basket)
/1981 Suzi GS650
/1988 BMW K100LT (in Lisbon)
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post #2 of 6 (permalink) Old Oct 23rd, 2013, 7:35 am
PsyKotic Waterfowl
 
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First thing I'd do is look into getting the fuel injectors serviced.
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post #3 of 6 (permalink) Old Oct 23rd, 2013, 11:47 am Thread Starter
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Hi Duck, Thanks for the note. Would you think they need to be changed to accommodate the exhaust, or maybe they are just dirty? Is this symptom common on any bike with injector issues? regardless of exhaust?

I do my own work so is this going to need a refresh kit? other parts?

Thanks again!

===================
/1957 BSA A10 Spitfire Scrambler
/1960 BSA A10 Super Rocket (basket)
/1981 Suzi GS650
/1988 BMW K100LT (in Lisbon)
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post #4 of 6 (permalink) Old Oct 24th, 2013, 7:39 am
PsyKotic Waterfowl
 
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I just recommend getting the FIs reconditioned as general maintenance item. Your fuel injectors are now 25-odd years old and have probably never been serviced. It's not something you can DIY as doing it properly requires an ultrasonic cleaner with a heated cleaning solution. In the US I use http://www.mrinjector.us/ for this but I've heard that many truck stops offer this service at an affordable price.

As to the issue of remapping to match the exhaust, the L-Jetronic is an analog device so my guess is that the Supertrapp is designed to work with the OEM mapping. Of course you could spend lots of money on dynos, regrinding the cams and all sorts of other mods like porting and decking but IMO I wouldn't bother.

Another thing to consider is replacing the boots above and below the throttle bodies as those get old, crack and leak air - leading to suboptimal engine performance.
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post #5 of 6 (permalink) Old Oct 24th, 2013, 11:25 am Thread Starter
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Thanks Duck, I will keep that site in my links, looks like a great idea at some point. I bet that was a big part of the "richness" of the exhaust on my other K. It always smelled of unburnt gas. I actually do have a tiny ultrasonic bath, but they have a good price for doing it right so I'll save up (time and money-wise) for that one sometime soon.

Quote:
As to the issue of remapping to match the exhaust, the L-Jetronic is an analog device so my guess is that the Supertrapp is designed to work with the OEM mapping. Of course you could spend lots of money on dynos, regrinding the cams and all sorts of other mods like porting and decking but IMO I wouldn't bother.
oh gods no, I just wondered if the L-Jetronic could self adjust or if the exhaust is specific to the bike (of course no one really knows what;s in there) but I wasn't thinking anywhere near all that nonsense! as long as she runs and keeps running, I'm not pushing the power envelope on this beast!! ;-)

In the end I have a suspicion that it is the battery at fault. After sitting overnight from a good long run it drops to 11.99 or 12V steady, and 11.4 if left for days. I will check into its levels and charge again, but coming from a full charge right to starting it comes to life relatively easily. Once running she's pretty good.

Thanks tons!!

===================
/1957 BSA A10 Spitfire Scrambler
/1960 BSA A10 Super Rocket (basket)
/1981 Suzi GS650
/1988 BMW K100LT (in Lisbon)
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post #6 of 6 (permalink) Old Oct 25th, 2013, 8:18 am
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A cheap Vacuum Gauge connected to each vacuum port in turn can tell you a lot about the integrity of the intake manifolds. And can tell you a lot more about the general condition of the engine, namely the valve train if you know how to read them. Easy...!

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