2KR with an EXUP valve??? And what 3LN1/2KR parts interchange?

Everything i've read suggests that in 1989 there were both the 2kr (non exup) and the 3ln1 models (with exup)
Mine definitely is a 2kr chassis and plated 1989, single front disk, twin headlights. However it has an EXUP valve in the exhaust. And I just pulled the CDI and it is labelled 3HX-82305-00 which is from the 2KR models

I have absolutely no history on this bike, no idea if the engine has been swapped, or just the exhaust or what. Were there ever any 2KR's made with an EXUP valve?
Chances are i'm going to need parts in the future and at the moment i'm not sure what fits what and if I should be ordering 2KR, 3LN1 parts or if it doesn't matter for certain things. I may need things like carby parts, intake manifolds, cables etc in the future. May even need a CDI which I notice has a different part number but same plugs (do they swap?)

 

Only photo I have at the moment

 

Engine # starts with 1HX. I believe the engines use a different oil filter design, and i'm not sure where the filter is on mine

The carbs... now I took the airbox off a couple nights ago, more accurately it basically pulled straight off with very little resistance, i'm unsure if the intake boots were even secured on there. And when I went to put it back on I thought how in the flap do you get this stupid thing on? It's by far the most retarded design i've seen as its next to impossible to really know if you've got all 4 on their respective carbs. I took the boots out of the airbox and tried to fit them individually, they are SO tight that I cannot get the damn things on all the way. I can get them on slightly skewed, but not seated (can run my fingernail around in the inside and feel theres a big gap on 1 side, always). I'm a pretty strong guy, and I cannot press them on all the way no matter how hard I try. And when I go to do up the clamp and then try and fit the airbox down on just '1' intake boot I can't do it, because of the lip it has to sit into. Doing it the other way (just pushing the airbox down, with the boots already in the airbox) seems impossible to get a proper seal due to no way to wiggle or stretch the intake boots

This makes me think that maybe the engine and certain bits have been swapped, including exhaust and carbs but not the airbox, and maybe there's a mismatch in the diameters. I know intake boots can be a little difficult to fit, but this is just insanely stupid
What I think i'll do is buy some radiator hose large enough to quite easily slip over the carbs and intake boots, cut into 4 short sections that slip over the carb and intakes, then secure them with 8x hose clamps. Or should I just completely piss the airbox off and use 4x pod filters?

 

Used rubber grease, no go. I can't physically stretch them over with my hands. Whats the easiest method, fit the boots to the carbs then wiggle the airbox on, or fit them in the airbox then somehow get them on the carbs? I'm still thinking I won't bother i'll just use radiator hose, that way I can get the correct size, mount them to the intake boots, then simply slip them over the carbs and tighten down some new hose clamps, piece of piss

 

Cool, radiator hose it is then. Hah

On another topic, I definitely need some new friction plates. Took it for a good ride today and if I race shift into 3rd there's a lot of slippage. Are the plates and springs the same for all the engines?
And does anyone have the tolerance specs for the springs?

 

Well, after pulling the carbs apart and comparing them to others listed. It seems mine are somewhat different in design and could very well be from a completely different bike. Here's a couple pics




Inlet outer diameter on carbs is 47.5mm, intake boots are about 44.5mm. This may explain why its practically impossible to fit them. No 'mikuni' markings on the bowls. Looks completely different to all the other pics i've seen
Needle: D4V1 / 3rd clip
Main: 72.5
Pilot: 17.5
Fuel screw???? I can't see them

 

This is what I have at the moment

Its just 51mm silicone hose pulled over the old boots, and extends down to the carbs. Effectively the stock boots are just resting on top of the carbs. The carb diameter is I believe 47.5mm and the (presumably stock) boots are about 44mm. Whoever the heck thought this design in general would be a good idea was probably on some serious drugs. My boots are in good condition and pliable but buggered if I can get them to stretch on the carbs. Maybe if I used a hydraulic press.....

This probably isn't the best method but it is incredibly easy. The hoses sit down on the carbs with almost no resistance, just plonk it in place then tighten the clamps. I thoroughly sprayed the area with starter fluid and had no change in revs, so they're sealing

What was your design? I didn't full replace the stock boots because I couldn't think of an easy and effectively way to make it seal the airbox side. Then again i'm not so sure I trust the stock boots either... they have a fair bit of play in the lip that sits into the airbox

 

It's on the air intake side, not the engine manifold. I'd imagine the pissy amount of fuel that gets shot backwards into the intakes would years to have any noticeable degradation to the hose. Judging by the amount of dirt in the carbs i'd say the stock boots weren't doing anything, very likely popped out on the first bump in the road. Would rather have silicone hose than useless intake boots that suck dirt on a daily basis

I somewhat suspect the carbs have been swapped at some point because the engine - while not spotless - was at least reasonably clean. The carbs on the other hand were absolutely filthy on the outside. I spent most of my time cleaning the outsides of them it was that bad, cleaning just the inside was pointless when as soon as I removed anything all the grease and dirt would just fall into the passages again

According to the 2kr manual they look similar if not the same, but different to this link http://2fiftycc.com/index.php?threa...0-3ln-bodywork-frame-engine-carburetors.3469/
Note the needle configuration looks the same on the 3LN6/7, but everything else is very different
So I wonder if any of the carbs had a different intake diameter. Maybe mine are from a 86 model or something which had a larger diameter, or maybe my airbox or intake boots were replaced with ones that had a different diameter

Anyone manage to get measurements of theirs?