Sunday, 12 February 2017

KTM 400 EXC 2002 - Keihin FCR39 Carb Issue

So my lovely little KTM just threw a hissy fit and started leaking from the overflow pipe on the bottom of the carb float bowl. When I first got this bike, I had to strip the whole thing down and rejet it, change all the seals and then set it up, it took awhile but since then it has been superb, with the engine always just right and better than any injected bike I've ridden to date. 

A simple fix I thought at first, strip it, clean it, rebuild it and hey presto. However since I did all of the above and it still leaked, I then looked at the settings and bought in a couple of new bits from Eurotek in Ripon, namely a seal for the float bowl and a replacement float needle. Once I fitted these I set about cleaning the float bowl again which is when I noticed the overflow pipe in the centre of the bowl was wobbly.

A bit of further inspection noted that it was actually cracked at its base, where it entered the alloy body of the float bowl. This was the actual cause of the leak and I've both never seen or heard of this before, so something new!

Some internet research took me to the Facebook group for KTM in the UK, a couple of helpful lads pointed me in the direction of KTMTalk, a US online forum for all things KTM, however the virus software on my computer won't let me open this as it hasn't been set up safely apparently, so I have no idea how useful it is at the moment. Further searches found me some more info though such as the part number for the non overflow float bowl, which isn't in my KTM parts manual for some reason and a full PDF of the carb and all the part numbers.

In the UK, I was also recommended to talk to Allens Performance in Nottingham, so I've emailed them too, along with FrankMX & JetsRUs, both of whom are in the US. JetsRUs appear to be having staffing problems and replied pretty quickly with the following: ''we have stopped international for the current time due to being under staffed sorry''. Tomorrow as it's a Monday, I'll try the UK KTM shops but I suspect that will be expensive, still it's gonna potentially be cheaper than a replacement carb whcih seem to be running between £500 - £1100 from what I've seen so far! I've been told they have to be ordered from Japan which takes awhile so we'll see.

JetRUs PDF: HERE. Part number is: Float Bowl Horizontal 1050-886-2100 021-264

I also found a discussion on ThumperTalk about whether or not the overflow is actually needed, but there was no real resolution to the discussion and as it was 6 years ago now, I doubt there will be! There were however pics of a version without the overflow at all.

So I'm now left with 3 options:
1. Hunting for a replacement float bowl for this carb
2. Find someone to solder the base of the pipe
3. Answer the question about whether it's actually needed and if not bung it up.

Money spent so far:
Float needle £12.85
Float bowl seal £12.35
Post £4.95

Lets see where this little issue takes us and hopefully I'll get it resolved before next weekend so I can go to Wales again!

UPDATE: 15/02/2017
So we piled a lump of Belzona 1111 around the pipe to seal the crack, unfortunately after 24 hours of setting, when I came to mount the overflow, it had a slight amount of movement in it, this then became a break as I tried to seal up the bowl and it basically fell out of the hole, so maybe I moved the pipe around a little during transport I have no idea, but this led me to start looking around again, specifically at Keihin in Japan, who I emailed and got a replay saying they don't deal with aftermarket requests and to contact a list of companies in the US.

I contacted Sudco and got a very prompt and helpfgul set of emails from a guy called Chad. The gist of this was that they did not have any of the overflow versions as they only supplied the non overflow ones for racing, ( because you can't have fuel spilling onto a track). The various OEM parts were adapted by each manufacturer to suit their requirements and so if you can't get one from them, then basically you can't get one.

However the upside was that apparently you can use the non overflow types in these carbs. Chad reckons any excess fuel should just go into the engine or out of the breather hoses. Ben, my local mechanic at Triple D KTM was hesitant about this. though. One comment given to me was that it would be necessary to turn off the fuel when the bikes not in use otherwise petrol will end up in the sump, which isn't good, although that depends upon the float and needle I would have thought? Whatever I'll probably give it a try and see what happens as to be honest a replacement carb is too expensive, so I might as well get an injected bike and move up the years if I'm going down this line and/or keep an eye out for a cheaper replacement in time!

The only other thing I've found out is that the Keihin carbs developed problems in later model bikes, which is why there aren't many parts kicking around now, there were several after market versions of the non overflow float bowl including various coloured but see thru versions...

So the story continues...

Update No:2 17/02/2017

So I've now got a replacement section of copper pipe to fit into the float bowl. I'll need to drill the hole out to 3mm to make it a tight fit and apparently glue it in place with Loctite 'Green' which is petrol resistant or any other petrol resistant glue. It could even be threaded so it screws into place. The angle for the internal pipe is slightly offset to the bottom part of the overflow pipe and the diameter is also different at 4mm with a small bulbous bit to make the plastic drain pipe sit on it better. This suggests that there are two sections of pipe, so when I drill it I need to be careful about the depth.

I also found something relevant on the Splat Shop website for Keihin PWK 28 carbs, (fitted to a Beta 290 Evo 2010 which I've just bought, more about this bike in a bit). These carbs leak at the overflow apparently... (mmm Keihin design weakness showing up here or OEM tinkering??);

''Many people complain about the amount of fuel these carbs leak and they nearly all mention that the Dellorto carburettor doesn't ever leak, this is because the Dellorto PHBL, as fitted to many trials bikes, does not have a overflow pipe so if the floats stop working for some reason it will flood your engine instead. If you really want to totally stop your carburettor leaking you can block the overflow pipe off, you run a slight risk of flooding your engine when dropping your bike or parking it up at a silly angle while walking a section but we have run a bike with the overflow blocked for 5 or 6 years without problems, another bonus of blocking the overflow is the brass overflow tube that stick out of the floats can be removed making it much easier to remove the float bowls.''

I'm busy for a few days now, so will get back to this next week...

Update No.3: 22/02/2017
So I got back to repairing the float bowl today. I took quite a bit of time setting up a drill so that I could drill out the little bit of copper pipe in the bottom of the tube, if i get it wrong I'm knackered so better to take it slow and be sure. Thankfully all went well and I've now popped in the replace 3mm pipe after carefully making sure it was the right length. it was sealed into place with some more of the Belzona 1111 and then left for 24 hours to cure.

I tested the float bowl with some neat petrol and woohoo no leaks!!

I refitted the whole lot and things looked good for about 10 minutes, bike running and all... Then the overflow started leaking again... Bugger!

So it's back in pieces again now, I've to clean out the needle jet hole with some compressed air and I think I'll need to check it for any corrosion in the copper parts. I may need to replace these too. I retested the float bowl repair and it isn't leaking even after 30 minutes sitting in petrol, so that repair is solid.

This is the latest culprit... there is a groove on the inside face of this where the needle has been rubbing against it over the years. Again it's not a part that is in the KTM parts manual, so back to keihin in the US to try to source the part or maybe have a go at filling the groove with Belzona and then polish it out. mmmm

Update no.4: Final one!! (err I hope)

So I found out what caused the groove in the brass piece from above when I fitted the service kit that I got from Frank MX on Ebay... (Great service by the way and you get a little packet of sweets too, Bonus!!)

Whenever I've fitted the carb back to the bike, I tried to make sure it was vertical, however I've always looked at this from the left hand side only and just gone with what looked right there. Today as I finished the final re install, I noticed the throttle cables were catching on the tank and not shutting off correctly causing the bike to overun when the clutch was pulled in on a test ride. the cables sit in a block and there are multiple bits sticking out fo the right side of the carb, which when you hang it vertical just be the left side means it actually sits with a very slight lean to the right, this causes the float needle to rub against one side of the brass inlet, thus causing the groove. it also means you have to mess around with the throttle loads to get it to work correctly and shut off. the final part of what I had done clicked today when I looked at the settings for the air mixture. I had set it to the same as the 250 carb I'd cleaned the other day, So 2.5 turns from closed, when for the 400 it is 1 turn from closed. Once re adjusted, I remounted the tank and plastics and the bike ran much better, shutting off properly now and not running fast.

Hopefully that is the carb sorted now for the foreseeable future, time will tell, although I think I will buy another of the after market air mixture threads and fit it to this carb.

Happy days, it's riding time again!!!

Another fettle!
After a couple of rides, the  bike was rnning rubbish again, so I stripped it again, gave it another clean and asked for some help on the forums. Several suggestions came back, I tried a few of them and nothing seemed to work, so I took the carb to Martin at MHB Motorcylces in Kirby Stephen. We stripped the carb after running the bike for a test run, then dumped it into a sonic cleaner for 10 minutes. Once this was done and uit rebuilt, we popped in a new spark plug and a new plug cap. This made the bike much better. At one point we had flames coming out the exhaust, which scared the dog a lot!

After ten minutes of air screw adjustment, we got it running reasonably well and left it at that.

I took the bike to Wales for the wekend, where if popped a fair bit to start out but then settled, (after flippingitself upside down in a narrow lane!) Once I'd done a full tank of fuel and washed out all of the cleaning agents and loose stuff, the bike runs so much better. It has changed significantly off the bottom end though, now tearing out my arms as it surges forward. Hpefully it'll settle back to it's softer power delivery over a bit of time! But it is running reliably at least for now.