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Old 12-18-2012, 08:18 PM   #1
Umarth OP
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Question Couple of LC4 questions

Got a few questions on the LC4 that I'm hoping some kind souls on here will be able to clarify for me.

1. Replacing the cam bearings, I inspected the cam shaft and noticed this:

That pin seems pretty rought arround the edges and I'm wondering if this is normal wear? Heavy wear? About done?

2. Taking off the radiators, I noticed that the two lower "tabs" that bolt the radiator to the frame have snapped off at the weld. Since this part of the frame holds oil I'm wondering if there are any special conciderations to weld them back on?

3. Is this normal and expected amount of gunk on a cylinder? If not, what would it be symptomatic of?


4. The spark plug's color, is it what it should be?


thanks guies...
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Old 12-18-2012, 09:08 PM   #2
gunnerbuck
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The plug looks like the proper light brown color...

The carbon deposit on the piston top looks pretty light to me though a bit tarry ... How do the deposits look in the valve passageways? Do the valves still sit above the seats or are they more flush with the surface {a bit recessed}?


The leading edge of your decomp pin does look pretty worn... I compared it to one I have sitting here that was so worn that it no longer engaged the cam: Yours looks like it is about 25% better than my completely shot unit... Was it still working? Did it make the klick to set itself when you rolled the engine over? If you plan to do a long trip with the bike then it would be worthwhile to replace the whole cam/decomp unit...
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Old 12-19-2012, 02:08 AM   #3
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Urmath, are you by chance running Holan crash bars on your LC4? This is related to the radiator mounting tabs...

Cheers,

Tseta
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Old 12-19-2012, 08:09 AM   #4
Umarth OP
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ah crap!

Quote:
Originally Posted by gunnerbuck View Post
The plug looks like the proper light brown color...

The carbon deposit on the piston top looks pretty light to me though a bit tarry ... How do the deposits look in the valve passageways? Do the valves still sit above the seats or are they more flush with the surface {a bit recessed}?


The leading edge of your decomp pin does look pretty worn... I compared it to one I have sitting here that was so worn that it no longer engaged the cam: Yours looks like it is about 25% better than my completely shot unit... Was it still working? Did it make the klick to set itself when you rolled the engine over? If you plan to do a long trip with the bike then it would be worthwhile to replace the whole cam/decomp unit...
Here's a pic of the head before getting it cleaned:


As for the pin, yup it was still doing it's job. But I'm leaving on very long trip in spring (100k+) so if it shows sign of needing to be replaced then I'll replace it. I only asked the question in the event that the pins always look that way and dont deteriorate past that point: no sense in replace parts just for the fun of it. I wonder if I could spin the pin arround? I could then carry it as a spare. Maybe...
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Old 12-19-2012, 08:10 AM   #5
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Quote:
Originally Posted by Tseta View Post
Urmath, are you by chance running Holan crash bars on your LC4? This is related to the radiator mounting tabs...

Cheers,

Tseta
At the moment, nop; dont have any crash protection on the bike.
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Old 12-19-2012, 12:34 PM   #6
bisbonian
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Even if the pin wears completely out, you can still use the decompression lever on the bars, right?
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Old 12-19-2012, 03:42 PM   #7
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Quote:
Originally Posted by bisbonian View Post
Even if the pin wears completely out, you can still use the decompression lever on the bars, right?
Yes you can... I believe the original LC 4 engine did not have an autodecomp at all and were kickstart only... When the E-start was added so was the auto decomp so both would work in harmony to keep the start procedure simple for the operator {just push the button}...
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Old 12-19-2012, 03:57 PM   #8
clintnz
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This was my pin after 95K km:



There was a very noticeable difference in ease of starting with the new cam in.

How many km on yours?

That carbon doesn't look too bad, like gunner says, maybe a bit tarry. Those valves look ok too. New ones for reference:



Cheers
Clint
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Old 12-19-2012, 04:36 PM   #9
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Quote:
Originally Posted by clintnz View Post

That carbon doesn't look too bad, like gunner says, maybe a bit tarry. Those valves look ok too. New ones for reference:



Cheers
Clint
Nice head Clint.
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Old 12-19-2012, 04:48 PM   #10
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The carbon build up in the combustion well looks minimal... Like Clint says, your valves look like they are sitting OK and not recessed badly into the seats... While you have the head off I would recommend that you have those valve seats touched up and replace the 4 valve stem seals... It's always a worthwhile extra measure to have the valve/seat interface refreshed while you have the head off... This will give you an as per new seal and the benefits that go along with it, like good power and good fuel economy for the duration of your travel adventure...

Also I would recommend replacement of the fore and aft mounting studs as it looks like some coolant has weeped in past the gasket and caused corrosion to get into the existing ones...


f
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Old 12-19-2012, 08:23 PM   #11
bmwktmbill
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Umarth,
You don't say what year your machine is?
I would drop the piston and inspect the bore for vertical scratches, if you see any the rings will need to be examined.

Me, I don't like that carbon and think it's heavy but I usually never overjet my engines(a raised needle is enough for me).

I bet your carb is over jetted or there is NO play in the choke actuation/cable. Just IMHO.
Clint and Gunner's opinions I respect on the carbon issue.
I swear I can feel an engine that is running 'fat'.

Do you have the two setting ignition for low octane fuel?

On a 40k trip you will need spares and tools and fresh suspension.

Like Gunner and Clint say, do the valve seals,cam followers and water pump.

I hope you figure out a way to turn the pin in the decomp.
We all need that.

I get excited just thinking about a 40k trip.
bill
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Old 12-19-2012, 08:58 PM   #12
Umarth OP
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bmwktmbill,

The bikes a second hand, unknown history, 640 adv 2006 with 30-40,000 km. Computer was replaced so I dont know exactly how many miles are on it.

Yup, the pistons are next on the list. I have not pulled it yet as I'm not sure if I need a special tool to fit it back in (to compress the rings) or if the bottom of the "sleeve" is tappered as on ktm's RFS engines. Any idea?

As for the carb being fat. Could be. I pretty sure that I reset every thing to factory specs when I rebuilt it a few months back. But then, I have zero exp with caburators so I very well could have f'd it up. The float I know I gotta go back and double check it, as I was not 100% clear on how to set the height. Had the tool but no instructions on how to use it. :p
As for the choke, good guess. WhenI got it, it was pulling hard to the point where turning the handle all the way left would kill the engine.



Quote:
Originally Posted by bmwktmbill View Post
Do you have the two setting ignition for low octane fuel?
Not sure what you mean by two settings. I know about the connector that toggles between premium and shit fuel. Is there more?

Quote:
Originally Posted by bmwktmbill View Post
On a 40k trip you will need spares and tools and fresh suspension.

Like Gunner and Clint say, do the valve seals,cam followers and water pump.
As for spares and tools i'm getting there very nicely. I'm taking a full gasket set for the engine, 2 carb and 2 water pump rebuild kits, 10 sets of valve cover gaskets, metal oil filters in the event I can't source normal ones plus a set of normal filters, 3 air filters, 1 full set of bearings (cam, wheels) and more shit that I forget.

The water pump is already done, cam followers also, remains the valve seals.
As for the valve seals, I'm not sure how to go about removing them. Is this an easy job or requires special tools?

Quote:
Originally Posted by bmwktmbill View Post
I hope you figure out a way to turn the pin in the decomp.
We all need that.
Thus I gather it's been attempted and failed... :(

Maybee I should start a pre-ride report just for the fun of keeping track of all the shit I've done to this thing to get it world ready. But then, it's been done already by others so I'll stick to
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Old 12-19-2012, 10:22 PM   #13
gunnerbuck
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For the valves your best off to order the four stem seals and take them and the complete head into a specialist and let him handle the rest... he will have the proper tools to measure the wear and see if the valves/guides are still within spec...
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Old 12-20-2012, 10:15 PM   #14
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Umarth,
Maybe you just need to check the bore by lowering the piston, the bore should look good to the eye, if you do pull the cylinder off you can recompress the rings with your fingers if you are careful, I have never broken one using that technique. Just feed the piston into the bore, It is chanfered.

The weight of the cylinder coming down the studs is a help but if you can find a helper that's nice too if she is beautiful.

Gaskets are a good call, carb parts, 1M of fuel line is always handy, tubes and tire stuff. I carry an electric air pump that's been used many times by myself and other riders I stopped to help. I'd carry a countershaft sprocket, a chain tool and replacement links, a couple of spokes, the used brake pads you have from replacing them with new just before you leave.

I carry a fan switch and a temp sender switch, lots of stuff I know but in many places parts just don't exist and have to be DHL'd in-DHELL.

That is never a good experience from what I know.
Do your suspension before you leave and carry the replaced seals, etc from the fork and the shock with you as emergency spares.

Blown suspension was the norm for half the travelers(or more) that I met in my travels. It's a real PIA and dangerous.

I don't know anything about the decomp pin, it scares me. Gunner, Clint and Tseta are the engine masters, my engine has not needed attention except for the usual top end stuff...yet(oh yah, I destroyed a piston too).
bill
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And high performance=high maintenance.
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bmwktmbill screwed with this post 12-20-2012 at 10:28 PM
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Old 12-21-2012, 01:09 AM   #15
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Bill, absolutely you can feel 'fat' jetting.

Biggest suspect for richness on a 20,000+km BST is needle jet wear.
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