Flat slide carby for KLX250

[PBMGold]

Anyone had experience with fitting a flat slide carb to that powerhouse known as 1981 KLX250?

Exhaust guy suggested a modern one from a Honda CRF150R but also not sure if that would be legal for an Evo bike.

[LWC82PE]

No its not legal. You would need to use a Lectron, EI or Mikuni TM.
In the 1980 White Bros catalogue they sold 34mm Dellorto pumper for the KLX

[PBMGold]

Oh well. It was worth a try.

I had a Dellorto Pumper carby back in 1980 on that KLX and all I recall of the pig of a thing was always bludging off my smarter mates (John Zordan are you still around?) to get it tuned correctly.

[grouty]

I have been tempted to put a Lectron flat slide on my KLX for sometime now. I already have one on each of my 390 Huskys. Brilliant carb, if a tad on the expensive side. Hence the reluctance at the moment to invest in another one. The only other issue is the height. It is no taller than the old SS carb as fitted originally. But the single cable enters the top rather than on the side as per the Mikuni. Lectron do a four stroke specific carb too.

[PBMGold]

I am tempting to try to find a suitable Lectron, but not sure where to start on this. Any idea of a model number and size?
In the meantime, the current configuration is running too lean and will stall if the throttle cracked open but is happy maintaining high revs. Thankfully, there is so little power I kind of ride with the throttle open everywhere and speed up and slow down with gear changes. Little effort on right hand required. Probably not the best way to improve ones riding skills.

I just had Tranzac do a new stainless steel pipe. Looks great and uses the modern idea of standard diameter at the cylinder head and then progressively gets fatter along the length of the pipe.

A very large motorcycle chain up here had a go at tuning the bike but I think they have become more familiar with injection and plug and play ECU and have forgotten the ancient art of carb tuning, as it is running no better now than it was before they lightened my wallet - considerably. Not happy.

Any KLX experts have advice on a good carb starting point, eg suitable jets. clip position etc. Bike shop have said they can't adjust the clip anymore for added richness so have given up.

Bribes and sexual favours happily negotiated to get this problem sorted.

[Curtis]

If you go on the lectron website it will ask for all your bike specs to help with what carb is required.
Alternatively for a more budget option you can run a mikuni round slide. Iv just done a full season of Vinduro on my KLX with no dramas. A pumper carb would be better no doubt, but the round slide works for me. I wrote my jetting specs on a piece of paper.....im still looking for it 

[LWC82PE]

If you email Lectron dimensions of your stock carby they will machine one up so it fits the stock manifold and airboot.

[grouty]

Or give Kevin a ring at Lectron. He is very approachable and helpful. I bought my Lectron's from Kelly at Motorsportz in the USA. He too is a valuable source of help and information.

There was a thread on here sometime ago reference larger pipes on the KLX. I seem to remember that the carb needed jetting down as it ran far too rich. I didn't have that issue as I fitted a Megacycle cam and special valve springs / collets. I found that the stock jetting was pretty much spot on with BOTH of these mods. I run an 1"1/2 dia pipe through to an old 430 Husky two stroke silencer. Although my cam was a mid / high range one, I also found that it produced an amazing amount of low end torque. At low revs it rides like an XT500 !  In the general scheme of things it is still gutless compared to a more modern 4 valve 250.

[The Stroker]

I ran a Delorto pumper on my KLX back in the day, it was great, paired with a super trap power pipe it ran like a dream and got rid of the notorious KLX flat spot.
I now run a standard carby with a 350 main and the needle on the middle notch. I have done all the mods ie; 262 piston, race cam staintune pipe, drilled holes in the air box, ride with my tounge hanging out of the left side of my mouth and the old girl gets along pretty well.

[cloggy]

You may mean  a 135. I posted the same mistake.
I had a new header U bend welded on. My exhaust expert tapered the pipe with an internal cone  as he didn't like the internal step from the narrow exhaust port to the pipe.
He didn't tell me he'd done that....
The pipe is the bigger kawasaki option.
Anyway the long and the short of it is it then ran rich everywhere except idle, where it was lean..... I now have a 132.5 main, new needle [top clip], an 08 needle jet and a 30 pilot. Could probably go to a 35 pilot , but then the main could be out again....
The standard carb has to be really close to optimum to work. One setting out and it makes it's feelings known. Although the shorter KL intake rubber will work with the carb and airbox one has to start from scratch with the jetting. It throws everything out.
The standard KLX is overcarbed, It's a 4mm hike up from a KL carb, and the same basic carb and size as an SP370 item.
I have a rollerbearing head but there was no difference when I changed from the standard plain head. I think the cam profiles are the same.
However I live in the damp wet Welsh Marches, with  the identical climate   to Grouty's Devon and very different from California and most of OZ

[FourstrokeForever]

The pipe is the bigger kawasaki option.
The standard KLX is overcarbed, It's a 4mm hike up from a KL carb, and the same basic carb and size as an SP370 item.

I've just acquired an '80 model KLX and am tinkering with the breed for the first time.
I couldn't believe how small the diameter of the stock pipe is....I've seen (Got one) XR75's with bigger pipes. Luckily I got a 1 1/2" header pipe in with all the parts that came with the bike. I just need to make up a tail pipe.

Second thing I was gobsmacked with is the tiny inlet port on the head compared with the size of the carb..... No wonder they don't have a reputation as a fast bike! The inlet manifold (from carb to head) is actually tapered down to meet the inlet port size. As it is, I reckon the bike would probably run better with a smaller carb......

In amongst all the parts I got with the bike, there are 2 spare motors, 1 KL and 1 KLX. Both these motors have a bigger inlet port on the head. Question: Were there any differences from 1 year model to the next or does my spare KLX motor have a KL head on it? The motor in the bike does have a completely different head on it as there is no access to the cam sprocket. Any idea what that might be off? I was told it was from a quad of some description...

Any help/info will be greatly appreciated.

[LWC82PE]

There is one big multi-page KLX thread on here called 'KLX a shared disease' and theres loads of info in there, inc info on using the KLF300? (or some kawa quad/trike) top end. I suggest checking it out as you will find plenty of info in there.

[Mick D]

Click here to access "KLX's - a shared disease"

[FourstrokeForever]

Thanks blokes 

[cloggy]

KLX motor had bigger valves and a much bigger carb, net gain 0.5 horsepower about 500 revs further up. This is already a stretched Z200....
I'm pretty dubious about aftermarket carbs in general and particularly for this motor. The standard carb if is anything too big for reasons previously discussed. Back in the day carb kits were routinely sold as upgrades. Why? well they made the shops a lot of money. Back then it was difficult to get alternative jets. It's dead easy now, not that some shops are capable of dealing with the reality......
Secondly during the production run of the XT/TT500 there was quite a bit of dyno work done on the standard motor. Result? well the perceived power boost of big bore carbs seemed to be down their being down on power in the lower  to middle rev range, which accentuated the extra 0.5 hp when they finally kicked in.
There's a successful tuner of XTs etc in OZ who maintains the standard carb is still the way to go, though he may be the only bloke on the planet to refurbish knackered old ones successfully.
 Thirdly if the XL185 is anything to go by the KLX is overpiped. I claim no insight but a commercial mate of mine who used to design and build one off paraglide exhaust systems reckons given the  port size the KLX actually needs a narrower pipe even than standard. He was pretty underwhelmed with the standard design saying that power is optimally down except at high revs. Well you have to rev the standard motor as there's not much torque.