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Discussion Starter · #1 ·
I have a 1985 Aspencade that has high compression 195psi in one cylinder, low compression 150psi in one cylinder and normal compression in the other 2 cylinders. I found a 1985 LTD motor that I can get for a very reasonable price. I do not know what the differences are between the motors. Can I swap these motors easily? I was given a price of $3500 to rebuild my motor. Is that reasonable?
 

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Yes, you can swap the motors with no problems.
How long have you had the bike, and does it run OK in spite of the compression differences? Have you done a leak-down test? That usually gives better info than a compression test.
You may be better off to keep your motor and have some head work done.
Anyway, welcome to the forum.
 

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The heads are different on the LTD, at least the right one is. Before you start putting out that kind of money/time, I think it would be worth it to at least pull the heads and inspect. Maybe it IS toaste, but wouldn't you kick yourself if a weekend and $100 would solve it?
 

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Welcome to the forum DavidBenJack

As Dennis said, we need more info, along with his questions,
How many miles on your motor?
Has it been sitting unused for a while? Did you do a wet compression check?
If it has been sitting, spray in some PB Blaster into each cylinder and turn the motor over by hand(rear plug at the stator, there is a bolt inside, turned clockwise only, let it set a day and turn over by hand again and squirt some more (in and around the pistons with the straw tube) and let set another day or two to loosen the rings that get stuck in the ring grooves from long term sitting unused. This will help bring the compression up unless you have a leaking head gasket.
 

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150psi doesn't sound low enough to change out an engine. Maybe 120psi would have me concerned, but 150 seems healthy enough.
 

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Discussion Starter · #6 ·
Thanks for the welcome and the information. The motor has 46,000 miles on it. It did sit for over six months before I got it. I was riding it and it lost power and was acting like it was running on 3 cylinders. That was when I took it to the shop. They replaced the plugs, told me one of them was wet and that I should not ride it with the high compression in one cylinder.
 

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Did the shop do the compression test? If so, I'd re-do it... all kinds of things can cause low compression, but high compression is odd. Could be more of a carb issue after sitting six months.
 

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A little gasoline in the cylinder would raise the compression.
 

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You are probably headed for head gaskets. If your getting any water in the cylinder the compression reading will be high because water won't compress well. I would't spend $3500 to rebuild a $2000 bike. The other problem is that the parts to do a good rebuild, like over sized rings aren't redally available. Anyone competent enough to do a rebuild on a wing would know treat.

Steve
 

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regardless of what they told you,how does mc run now that they replaced the plugs?
personally depending on a shop to tell what is wrong and quoting me $3500 to rebuild i'd have to be looking for a 2nd opinion

for that kind of money you could purchase another 1200 in good shape,what part of florida do you live in
 

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Anything in the combustion chamber will raise the compression, including carbon build up, which is the most common cause, but gas or coolant would certainly do it. Your numbers are unusual. One high, two normal, and one low. I agree the low one is not too low, but the differences will make a difference in how smooth the engine runs, and will make it impossible to synch the carbs accurately.

I have an LTD, and there is a difference in the engines. I had so much trouble with the fuel injection (actually finding parts for it, it works fine when everything is ok, but all the rubber parts on mine were rotted out, and there are a LOT of them) I wanted to switch to a carb setup, but was told it couldn't be done, something to do with the ignition timing if I remember correctly. My engine had 170 psi in all 4 cylinders when I first got it, haven't checked it since, but it still runs good, idles nice and smooth.
 
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