HELP! K1100 LT feels like its being held back.

[Temple2286]

Firstly HI. This forum has resolved so many problems that I 100% thought I would never need to post. Full disclosure I have no idea what I'm doing everything I have learnt is from YouTube and this forum, so once again thankyou.

Back story brought the bike 2 years ago; rode once before the tear down and had a couple of experiences that almost felt like the bike wanted to ride it self and take off. Put it down to a potential sticking throttle or injectors coming on and off. Wouldn't be a problem because it was getting torn down and those parts would be replaced.

The problem. Bike fires up exactly as you'd exspects. Problem seems to appear once up to running temperature after 5 to 10 mints of riding (still don't know if this is temperature related). After a while the bike almost feels like its under powered stutters (does not die). Bike almost feels like it is restricted power kicks in every now and again for a moment which is why I use the term under powered. Every now and again there's a misfire which only seems to come on under load but not always.    When fully cranked open there's a clear sound change but bike almost reaches a ceiling and just gets loud. Almost struggles to want to put out any more than 70mph. I have wired up a new Speedo and have yet to fully confirm it working but if that’s anything to go by the revs are not creeping anything over 3000rpm.

What I've done:
Originally thought it was being starved: new injectors, new spark plugs cleaned all fuel lines.
- came across a post mentioning similar symptoms about failed hall sensor (of which has been changed thinking that must be the cause)

[Laitch]

Welcome to Motobrick, Temple!
In which year was your Brick manufactured? Try to post some photos of it.

[Temple2286]

It’s a 1993 k1100 LT

[frankenduck]

Easy peasy. If it's a 93 then you should renew the heat sink compound behind the ignition amp.  When that gets old the ignition amp gets too warm and impacts performance.

The ignition amp is located on the front left of the lower battery tray.



1 - Remove the ignition amp.

2 - Sand off old heat sink compound.

3 - Apply new heat sink compound.

4 - Reinstall.

Note: This only applies to 4V K (K1100, K1, K100RS4V) 93 and earlier. 94 and later K1100s do not have the ignition amp.

[Temple2286]

So currently the bike has the loom from a donner k1100 in it. The original loom had been butchered by the previous owner trying to temove the lunchbonlx and abs i couldnt make heads or tails of it. From what I can tell the later k1100 has the ignition amplifier under the fuse box which being from a newer k1100 I believe a 98.

Now you mention the ignition amplifier and I've read up a little the symptoms sound right. Always surprising me how many rabbit holes there are when you know what to look form.

 My question though is all other electrical and ignition parts bar the coils are from the newer k1100 which showed non of the symptoms. Should that not mean the older amplifier is not needed? Can I just plug an older one in ?

What I havent done is actually checked the plugs since fitting the new ones (one of my jobs today) my think is I don't actually know if the coils are bad or if I get a spark on all cylinders.

[frankenduck]

Well that complicates matters a bit.

What Motronic does it use?

[Temple2286]

I wouldnt want to disappointed and keep things simple. Currently has the motronic pictured below. (From the donner)

Just pulled the spark plugs to make sure all were sparking (which they did) however 1 and 2 are very black and 3 and 4 were almost clean. The plug connectors on 3 and 4 felt almost loose almost like I hadn't connected them properly.

Could this be the culprit? In essence each coil is only firing 1 cylinder each ? Going to take it for a spin in a second and see if that made any difference.

[Temple2286]

Looks like it was a loose connection between the coils and the spark plugs on 3 and 4.

My lack for attention to detail and experience has clearly shown off. However there is always a silver lining thank you frankenduck I didnt know about the 93 lt ignition amp and I learnt alot about hall sensors and jets from this forum while trying to diagnos.

[frankenduck]

Yeah, the spark plug leads needs to be firmly attached on all K bikes. What I do is grab the tang on the spark plug cap with pliers in one hand and then hit that hand with the other to get them well seated on the spark plugs.

[sooprvylyn]

Make sure your spark plug cables are tight. As they age the connections can become loose, and you'll end up w those fouled  plugs. If they don't all feel equally tight on the spark plug bobbins it might be time for new wires.