Which Would You Buy

Seeking advice on the durability of the XJ700 engine. Ebay has several for sale, various prices but all about the same. There is one with relatively low miles (less than 15,000) but it is not listed as running. The shop holding it says it came in sans bike as it sits in the ad. They did state that it is un-damaged externally and spins freely, and that they would perform a leak down and compression test for me to reassure me that it works. There are others with mileage in the 25-35k range or higher, which are listed as known running, some of the ads even have embedded videos which show the engine running. Research on the forum reveals several discussions about the potential for the XJ engine to have second gear issues and deteriorated primary chain guides in higher mileage engines so I am hesitant to sink my money in a bike with less life left in it.
Needless to say in any case I would check valves and bring them into spec as necessary before installing in my bike. Oh yeah, this was the bike with the engine full of rain water, I am jumping on a cheaper faster option to get this bike running again while I consider building the original engine.
Which one to choose?

 

Well just by going for the 'bird in the hand' maxim I say the running one. since you still have the rebuild project that could be the back-up 'good one' if need be..

James

 

i'd go for the leak down test. with low miles. known running is a lot of different things to different people. the videos show some engine running, might not be yours though.
the chain guides, i think is a matter of age, not miles. how many decades have the lived in oil, yuck

 

I voted for the 25k+ and running, mostly because that describes my bike exactly as I bought it, and I couldn't be happier with it.

However, more info never hurt anyone. Unless the info is regarding how to hurt someone. Right.

 

The shop with the low mileage engine called me, said they had performed a leak down for a previous customer who backed out of the sale and gave me the results. Results for all four cylinders were just under 10% loss, so that works for me. Given that they never had an ignition or carbs with it, they never tried to run it, so I guess thats still a gamble but I think its worth rolling the dice, since I have all the parts that came off my bike.

 

When I bought my 700, it had 33400 miles on it. Right now it has 47796.3 miles and the speedometer was broke for 4 years. I don't think it's so much the mileage as it is the maintenance.
If it runs, you have something to work with. Either way it's a crap shoot.

 

The chain guide thing is why I can't trust any XJ "shaftie" that hasn't had it replaced.

Polock is right; it's age-related and mileage-agnostic. When they fail, they fail; whether the bike has 6K or 60K on it. Lots do; some never do. Why is as yet elusive.

Other than that, I would go by the compression and leak-down tests. EQUAL (or close to it) readings are more important than actual numbers, unless they're seriously low or way too high (indicating problems.)

Good compression numbers, all within 10% of each other, and solid, even, leakdown tests should be the deciding factor.

The chain guide thing is a crapshoot. Since the motor's out of the frame, I'd go ahead and replace it. You don't need to break down the top end for that.