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Old 06-04-2013, 04:03 AM   #1
morini OP
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New KTM 640 Adv owner - carbs and main bearings

Last fall a friend persuaded me to buy a 1998 KTM 640 Adventure. I have always been good at convincing myself that I need another motorcycle, but this kind of bike was new to me. What helped my argumentation (mostly to my wife, since I had already bought the bike unseen), was the low milage (14000 km) and the price being 2/3 of the market price here in Norway. My friend said he would buy it from me if I did not like it and several people have contacted me via the previous owner to try to buy it, but I have no plans for selling.

Here she is (top luggage box of previous owner is of course discarded):


The KTM is very different from my other motorcycles:
’76 Moto Guzzi Le Mans I 850
’80 Moto Guzzi 850 T3 California
‘78 Moto Guzzi SP 1000, Café Racer
’74 Moto Morini 350 Sport
’90 Honda GB500 Clubman (wife’s)
’64 Royal Enfield 500 Bullett (ridden from New Dehli to Norway – so maybe I belong here on advrider?).

I have been riding bikes for 25 years (since long before I was old enough:-)), and since my first meters on two wheels I have dreamt about doing a RTW trip. I am slowly realising that this dream is completely incompatible with how I live right now, but the KTM is keeping the dream alive. It is a completely new kind of bike for me. Very fun indeed, but I have a lot to learn about offroad riding.

So far I have not ridden the KTM much, but I have some questions to this knowledgeable forum:
  1. I understand that the main bearing was an issue on these early bikes. Is there any way of knowing if a used bike has had the upgrade (there is no receipt for this)?
  2. She looks good and runs strong, but is simply impossible to start when cold. I have tried all the different starting procedures described here on the forum, but I am dependant on starting gas to get her going. I have now stripped her and plan to adjust valves, renew spark plug and clean the Dellorto PHM40. Damn it is cramped in here! Are there any other smart things to do while I am at it? I am tempted to install a TM40 or FCR 39 – are these worth it compared to the Dellorto?
  3. I am considering a slip on from Akrapovic or Leo Vince (cheaper). According to KTM Sommer the Leo Vince gives less performance than original (but they are selling Akrapovic). Does anybody have experience with Leo Vince?

Eternally grateful for any tips that can help me get my KTM going.

Greetings from sunny Oslo!
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Old 06-04-2013, 09:58 AM   #2
Kawidad
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Quote:
Originally Posted by morini View Post
Last fall a friend persuaded me to buy a 1998 KTM 640 Adventure. I have always been good at convincing myself that I need another motorcycle, but this kind of bike was new to me. What helped my argumentation (mostly to my wife, since I had already bought the bike unseen), was the low milage (14000 km) and the price being 2/3 of the market price here in Norway. My friend said he would buy it from me if I did not like it and several people have contacted me via the previous owner to try to buy it, but I have no plans for selling.

Here she is (top luggage box of previous owner is of course discarded):


So far I have not ridden the KTM much, but I have some questions to this knowledgeable forum:
  1. I understand that the main bearing was an issue on these early bikes. Is there any way of knowing if a used bike has had the upgrade (there is no receipt for this)?
  2. She looks good and runs strong, but is simply impossible to start when cold. I have tried all the different starting procedures described here on the forum, but I am dependant on starting gas to get her going. I have now stripped her and plan to adjust valves, renew spark plug and clean the Dellorto PHM40. Damn it is cramped in here! Are there any other smart things to do while I am at it? I am tempted to install a TM40 or FCR 39 – are these worth it compared to the Dellorto?
  3. I am considering a slip on from Akrapovic or Leo Vince (cheaper). According to KTM Sommer the Leo Vince gives less performance than original (but they are selling Akrapovic). Does anybody have experience with Leo Vince?

Eternally grateful for any tips that can help me get my KTM going.

Greetings from sunny Oslo!
I'm sure others with more knowledge will comment, but here's my take on it.

#1: I don't know of any way of checking without looking for yourself. However, I don't think I'd worry about it too much. Normally if it starts to go, you get a warning with excessive noise before a total failure. Of course, popping the side cover off to look is not difficult if you're concerned.

#2: From everything I've read the Del Orto is not a very good carburetor. The newer BST40 is not a very good one either, but is better. I have the BST40 and can feel the limitation of the carb on the engine. However, it is a simple and reliable unit that with some care (ie: putting a filter on the breather pipe) should give long life. The pumper carbs will deliver much better performance, but are more temperamental and more complicated. The first I'd do, and did with mine, is pull the carb off and carefully inspect it for wear and/or damage, which can occur in surprisingly low mileage.

#3: I had a Leo on a previous bike and thought it was a good piece of kit and a good value for the money. However, I have no experience on this bike. Mine has an FMF Q4, which came with the bike.
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Old 06-04-2013, 10:56 AM   #3
morini OP
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Thank you for your reply! I spoke to KTM Faber in Germany today and he claimed that the Dellortos had such a wide quality spread that they were hopeless to work with. The BST40 was according to him the best carburettor for a standard engine. The MT40 combined with Akrapovic would according to him give too much performance for the weak bottom end of the LC4. He claimed that the normal life expectancy of a standard LC4 was no more than 20 000 km (ca 12 500 miles)!

Suprisingly pessimistic considering the RTW trips which have been done with these engines.
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Old 06-04-2013, 11:42 AM   #4
flatchance
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LC4 = 12,500 mi ???

Mine has 44,732 mi.and going strong!
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Old 06-04-2013, 11:42 AM   #5
DSM8
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If you can use the same carb that was put on the US Spec 2004 624 SXC.

I had the 640 and then the 625 and going from a CV carb to the pumper carb made such a huge difference in performance and ride-ability it was night and day. If I had done that to the 640 I had it would have never left my garage.

CARBURETOR FCRMX-41

Manual: 088226, Page Number: C04583310_088226

Taken from parts fisch on Munnracing.com
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Old 06-04-2013, 03:02 PM   #6
clintnz
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Great looking machine!

Quote:
Originally Posted by morini View Post

So far I have not ridden the KTM much, but I have some questions to this knowledgeable forum:
  1. I understand that the main bearing was an issue on these early bikes. Is there any way of knowing if a used bike has had the upgrade (there is no receipt for this)?
Just to clarify, it is the left side gearbox mainshaft bearing that can be an issue, the one behind the clutch. If you take apart the left side to the point of removing the clutch you will be able to see the bearing & know what you have - the original is a ball bearing, the upgrade & '03+ have a roller bearing.

Can't help much on Dellorto's sorry. If you can get a BST40 cheap they are an easy carb to work on, but they are wear prone & you get much better throttle response off an FCR. So if the cost isn't too different I'd go FCR. I think you have to watch for clearance vs the exhaust with an FCR on the earlier LC4's - a new exhaust would likely fix that but do check.

Quote:
Originally Posted by morini View Post
The MT40 combined with Akrapovic would according to him give too much performance for the weak bottom end of the LC4. He claimed that the normal life expectancy of a standard LC4 was no more than 20 000 km (ca 12 500 miles)!

Suprisingly pessimistic considering the RTW trips which have been done with these engines.
Surprisingly pessimistic alright! Maybe they have seen an unusual number of the mainshaft bearing failures & a few of the low km's cam follower bearing problems that hit a few later model motors? These issues are certainly not universal, or unfixable however.

My engine did 50 000km before needing a little work: (starter clutch, cam bearings & waterpump rebuild) Then it went happily until 95 000 km when it got a major service - the big end bearing had worn out plus the piston, cam & valves all needed attention. So just a little more than 20K km!! I don't think there are too many bottom end differences 98-07 (someone please correct me if I'm wrong )

Cheers
Clint
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Old 06-04-2013, 04:24 PM   #7
BillyD
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Morini:

Welcome. You and I have similar tastes in motorbikes. Plus, I'm Norwegian, albeit only by heritage.

+1 on the main shaft bearing, which was originally a ball bearing that later got changed to a roller bearing (2003?). Easy to change, if you have a puller.

I got the BST to work reasonably well on-road, but off-road it left a bit to be desired. It doesn't like whoops very much. Plus the bits and pieces aren't very durable, especially in dusty off-road conditions.

I'm on my third 640 and have changed them all out to Keihin 41 FCRs: Two were FCR Single carbs and one a FCRMX. I went FCRMX this last time around simply because I ride it mostly off-road (bigger float bowl with baffling).

And, I'm running a LV silencer with spark arrestor. The spring loops on the mid pipe and silencer don't line up exactly, but close enough. I don't think Carbon Fibre is an appropriate material for the hanger clamp on an off-road bike. The dirt and grime gets in there and wet sands its way through the CF bands. I've replaced the clamp once and will source a steel one the next time around. Other than that, the build quality on the LV is good.
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KTM '08 690 RFR, '08 990Adv S (carbs), '07 640Adv, '03 540EXC, Ducati 851, Moto Guzzi 850 Lemans, Ercole & 2VT and Yamaha RD350.

BillyD screwed with this post 06-04-2013 at 04:30 PM
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Old 06-04-2013, 11:11 PM   #8
bmwktmbill
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Quote:
Originally Posted by morini View Post
Thank you for your reply! I spoke to KTM Faber in Germany today and he claimed that the Dellortos had such a wide quality spread that they were hopeless to work with. The BST40 was according to him the best carburettor for a standard engine. The MT40 combined with Akrapovic would according to him give too much performance for the weak bottom end of the LC4. He claimed that the normal life expectancy of a standard LC4 was no more than 20 000 km (ca 12 500 miles)!

Suprisingly pessimistic considering the RTW trips which have been done with these engines.
Morini,
I am getting close to 100K km and have the BST40 on my '02 640a.
I have replaced the carb slide components once, the needle a few times.
My machine went RTW through Russia and Mongolia, etc.

My fuel consumption is around 45mpg(dont know km/L conversion)

My lower end is still solid. I did break a top ring and destroyed the piston because I ran poor gas and lugged my engine too much.

Enjoy your new motorcycle(it looks great), keep the revs above 4000 rpm and use the best gas you can afford. Some members use regular gasoline rather than premium but keep the revs up to avoid detonation.

One thing some of us do is run 17/42 gearing. Gearing up at the countershaft lowers the revs at crusing speed and helps with engine vibration.

You might consider a centerstand?
bill
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"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
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Old 06-05-2013, 06:53 AM   #9
morini OP
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Thank you for reassuring words about milage. With the planned purchase of carburettor, exhaust and seat my uprade would soon reach 50% of the price I paid for the bike. It would be sad if the engine should blow up shortly thereafter.

I'll probably go for the TM40 carburettor, Leo Vince or Akrapovic silencer and Renazco seat.

For a start:-)
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Old 06-05-2013, 11:52 PM   #10
bmwktmbill
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Quote:
Originally Posted by morini View Post
Thank you for reassuring words about milage. With the planned purchase of carburettor, exhaust and seat my uprade would soon reach 50% of the price I paid for the bike. It would be sad if the engine should blow up shortly thereafter.

I'll probably go for the TM40 carburettor, Leo Vince or Akrapovic silencer and Renazco seat.

For a start:-)
Morini,
I have the all leather Renazco, so does my son on his 950 Adv.

The leather seat is extremely comfortable and rides dryer in the rain than any vinyl seat.

I am so spoiled now if I had to ride on a plastic seat I think I'd cry.
bill
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'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
Bill Shockley
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Old 06-06-2013, 05:22 AM   #11
Hipster
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Morini,

Here's a good source for the Mikuni TM40 carb http://www.nichecycle.com/ncs/index....-acc-pump.html
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Old 09-02-2013, 07:39 AM   #12
morini OP
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Thank you for all the replys. Since my last post I have gotten a heir for all my motorbikes so I have been busy changing diapers:-)

After speaking with different specialists in Germany I am confused regarding the Dellorto carburettor. Some claim it is good, while others say it is useless. I have gotten some offers on FCR carbs, but they are all 41mm. I have read that there is something called a hi flow head on these models, and since mine is an early version ('98) I guess i do not have that. With no Hi Flow head I suspect that the 41mm carb would be too big and a 39 will give better mid-range performance. Any opinions on that?

I understand that I will have some work adapting the twin cables of the FCR or TM40, but are there other challenges involved (besides jetting)?
Will the TM40 or FCR 39/41 fit the air filter intake without modification?

Regards from sunny Oslo!
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Old 09-02-2013, 11:38 PM   #13
bmwktmbill
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Morini,
Guess I'd put a BST 40 on it, be done and ride it(unless you are a racer).

That carb is not much of a problem and self compensates for altitude changes so the Alps or other mountainous areas are no problem.

Gas mpg is excellent.

Parts are available from KTM.

bill
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'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
Bill Shockley
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