Hi Guys,

I'm back after a 2 year delay (due to selling my beloved K100RT and buying a Kawasaki GPX600R).

I swapped the GPX for a 1984 K100RS and am now happy again ... or at least would be, if it ran right.

The bike had been stood a while (ie 3 years), so I checked compression, lubricated cylinders, renewed plugs, battery, air filter, oil, coolant, and rode it home (a distance of 15 miles).

Problem is, it's short of power, and backfires.

It seems to not fire on Cylinder 2 (ie, seocnd from left looking at LHS of engine). The exhaust leading to Cylinder 2 is cold/lukewarm no hot as the other 3 are.

I have checked for spark - all OK big fa spark. I am suspecting inectors need cleaned, although I have cleaned them bu putting 12V to open them (sealed with rubber to prevent fire etc) and squirting injector cleaner ... but this is not the full ticket, I realise this.

Th spark plug to Cylinder 2 is wet with fuel, indicating that the injector is working, and I have spark at No 2 as well. Strange. All other plugs are fouled (oilycolour) even though they are brand new.

Some previous owner (or previous to him ), had implemented some very creative wiring solutions. The VDO Voltmeter was wired to the starter (now wired by me to the accesory loom), and the EFI Relay had a bodged bit of wire from Pin 86 also going to the starter. Needless to say this has been removed.

I have tested the EFI relay and it works. Also tested the EFI Connector (EFO Computer) at Pin 12, etc ... all good.

The bike is backfiring at idle, and totally lacking in power ... but I cannot adjust the TPS as the mounting screw is completely seized on the nightmare far side. I have also disconnected the TPS and tested but no improvement.

Fuel filter? Injectors? What is the correct set up/order for the HT Leads/spark plug wires? The mysterious previous owner marked them with paint in an "abstract art" kinda way ... and has totally confused me as to which lead goes to which plug, from the coils.

Any ideas I'd be most grateful where to start with this lovely old K.

Best wishes,

Steve

The ignition is working with a wasted spark...firing on every revolution...one coil serves cylinder 1 & 4
the other cylinder 2 & 3.

Try to swap cylinder 2 and 3 at the coil terminals, if the problem moves to #3...the coil is your bad guy
(check the output terminal for corrosion, also).
If the problem is still at #2, the check wire, cap (and plug, could be a bad one in the batch of new ones).

Inge K.

we've seen some bad plugs too, so change them out with new ones. The backfiring sounds like a vacuum leak, so I would spray carb cleaner around each rubber boot at the throttle bodies. If your situation improves, that will be the area needing attention. Also the rubber tube between the block and TB's is prone to cracking and will leak air into your system.

When I bought my 85 RT, it too had been stood for a while and would only run on three cylinders. I checked the plugs first and found No. 3 was very black , the rest looked normal. A new set of plugs cured the problem. I hope yours turns out to be something as simple.

Regards, Ralph.

Tell us a bit more about the plug leads/plugs - Plug leads look good inside the plug connector? And the plugs have their little bobbins screwed on? Can you measure compression?

Problem solved ... ish.

Thank you guys .... I traced the HT leads/spark plug wires and found they were in the wrong order. The previous owner labelled them in sequence left-to-right and fitted them that way, instead of in the firing order.

I swapped them around and wow! No more backfiring, bike is revving freely, and idling steady, and accelerating like a dream

However there is an intermittent slight slight hesitation/"missing" at idle.

Just before typing this, I found a post by Larry S that confirms the firing order of the K100 to be 1-3-4-2. So I think I need to double-check my HT Leads/spark plug wires are correctly fitted in case I have one wrong.

Re: idle speed, am I right in saying the idle-stop screw is the larger screw in the centre of the throttle bodies and the idle adjustment screw is the smaller one above and behind it? I need to adjust the smaller one as well, as the bike simply won't idle any lower than 1050-1100 rpm using the other one.

I also need to re-adjust the TPS as it won't click now, no matter how much I turn it in either direction.

Spark plug wires is normaly labelled by cylinder #, and not in firing order.
The larger idle stop screw is the idle adjustement, the smaller one is the butterfly link screw,
which is set at factory and should not be disturbed.

With to high idle and not possible to set the TPS, check the free play at the choke wire (it just raises idle).

Other causes for to high idle could be: intake leak (use propane in suspected areas to check),
or throttle bypass screws out of syncronisation.

Inge K.