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Old 04-18-2013, 04:36 PM   #1
lost1 OP
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LC 4 engine no compression

I bought an 03 640 engine with 13000 klms that I can't get to run. After carb cleaning, spark check, timing check and fuel check I realized that it must be something else. I did a compression check (I know the auto decomp was on) and got a whopping 30 lbs.

based on personal experience what is the most likely scenario. Broken rings, stuck valve, holed piston, cracked cylinder or what ??? Just a minute, let me get a box of Kleenex and my credit card.

The only info I got from the previous owner was that it had a head gasket leak which was repaired and it never ran again.

Thanks
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Old 04-18-2013, 04:55 PM   #2
gunnerbuck
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Quote:
Originally Posted by lost1 View Post
I bought an 03 640 engine with 13000 klms that I can't get to run. After carb cleaning, spark check, timing check and fuel check I realized that it must be something else. I did a compression check (I know the auto decomp was on) and got a whopping 30 lbs.

based on personal experience what is the most likely scenario. Broken rings, stuck valve, holed piston, cracked cylinder or what ??? Just a minute, let me get a box of Kleenex and my credit card.

The only info I got from the previous owner was that it had a head gasket leak which was repaired and it never ran again.

Thanks
Could be any number of the things you mentioned, or maybe a bent valve... Your best to just dig in, pull the top end and inspect for defects...
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Old 04-19-2013, 10:41 AM   #3
biensur22
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One option is to drip a little oil in the sparkplug socket and kick it through a few times. Check compression again, if it goes up this suggests bad rings, if nothing changes you're looking at valves or piston.

But like gunner said, you won't know until you look. Auto-decomp shouldn't drop it below 100.
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Old 04-19-2013, 11:27 AM   #4
lost1 OP
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It's dead

Ok, we'll the damage is pretty clear. Piston fragmented on the intake and exhaust sides. The cylinder bore is deeply pitted. The rings broke and hammered the cylinder head. The valves and seats appear unmanaged so next plan of action is to see if this 2003 hi flow head is ok to swap onto my 2001 cylinder.
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Old 04-19-2013, 06:15 PM   #5
gunnerbuck
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Originally Posted by lost1 View Post
Ok, we'll the damage is pretty clear. Piston fragmented on the intake and exhaust sides. The cylinder bore is deeply pitted. The rings broke and hammered the cylinder head. The valves and seats appear unmanaged so next plan of action is to see if this 2003 hi flow head is ok to swap onto my 2001 cylinder.
The 2003 head will mount onto the 2001 cylinder with out a problem... But if you plan to use the 2001 cylinder on the 2003 bottom end then you will have to make some dowel reducers... The 2003 has much smaller gasket surface alignment dowels than on the 2001... Here are some pics of the mods you need to make to fit an 01 cylinder onto an 03 or later:



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Old 04-19-2013, 08:48 PM   #6
lost1 OP
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Thank you. That there is some
good info.
I will take the entire cylinder head, cam, rockers etc. I hope that the timing chain length is the same. I will also use the Hi Flow exhaust and will poach a
few other items from the 2003. Do you think the bst carb jetting will be the same? I could use the the TPS from the 2003, but then I have to change
wiring and ecu?

I can use whatever I want from either the 03 and 01
adventure 640. I just want to make sure that I get the best from either. For the most part the bikes are nearly identical. I have an emotional attachment to the 01 as it got me from Australia to Thailand
overland.
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Old 04-19-2013, 10:04 PM   #7
gunnerbuck
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Quote:
Originally Posted by lost1 View Post
Thank you. That there is some
good info.
I will take the entire cylinder head, cam, rockers etc. I hope that the timing chain length is the same. I will also use the Hi Flow exhaust and will poach a
few other items from the 2003. Do you think the bst carb jetting will be the same? I could use the the TPS from the 2003, but then I have to change
wiring and ecu?

I can use whatever I want from either the 03 and 01
adventure 640. I just want to make sure that I get the best from either. For the most part the bikes are nearly identical. I have an emotional attachment to the 01 as it got me from Australia to Thailand
overland.
The Hi Flo runs a bigger M jet, stock main is 152.5 Vs something like a 145 on the 01... The cam chain and related sprockets are the same... Make sure you have an 03 main roller bearing in your 01...
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