Jug Swap

I'm working on a budget and have the engine apart. my mechanic is telling me my jugs need machined and its going to be a fair bit to get them over bored. I've found a set of jugs on eBay that are supposed to be in good shape and the seller has confirmed that they don't need machined, hopefully that's true. but the question is, are the jugs on an 82 650 maxim interchangeable with an 83 650 seca turbo?

 

I can't answer the question, but I can ad more things to consider before jumping in.
If the bores are not serviceable, the pistons and rings would also be suspect.
So even if the bore problem can be solved whith a Maxim set, the pistons for a lot of factory turbos were different as well.

 

I agree, if your cylinder walls are crap - your pistons/rings are probably not in too great of shape either, so even with new, usable jugs - you might still have to get new pistons/rings.

If you ended up throwing some money at overboring, you need new pistons and rings as well. How much are you going to end up farting around before you just come to the conclusion you need a top-end rebuild?

Sometimes the direct path ends up being cheaper than skirting the issue. Just sayin

 

pistons are fine. poor compression on cylinder 3 started the tear down. already planning on new rings. there is one bad scratch in cylinder 3 that my mechanic is saying won't come out with a good honing. so i'm looking at a few hundred dollars for machining then over sized pistons or 50 ish for another set of jugs if they are interchangeable.

 

Before you took it apart, did you check your valve clearances to determine whether or not it was sijmply a shim-clearance issue?

dave

 

If they did a correct wet/dry comp test, valve issues would have been diagnosed without fail.

 

Something caused this, so at the very least the #3 piston is questionable.

At this point, the CHEAPEST solution would be:

Find another set of cylinders from a MATCHING bike, not a turbo or anything else. You should be able to find a set from a relatively low-mileage motor, as many of these bike get parted out.

Measure the used set of cylinders for bore, taper and out-of-roundness; and check your piston clearances for the other 3 pistons. If all is good, get the replacement jugs honed, replace the #3 piston and the rings on all 4 and be done with it.

MUCH cheaper than an overbore and then trying to find and afford 4 new O/S piston and ring sets.

Then, since the head is off; lap the valves and replace the valve stem seals.

IMHO; at least that's what I'd do in similar circumstances.

 

Something caused this, so at the very least the #3 piston is questionable.

At this point, the CHEAPEST solution would be:

Find another set of cylinders from a MATCHING bike, not a turbo or anything else. You should be able to find a set from a relatively low-mileage motor, as many of these bike get parted out.

Don't know if this is a solution for you, but I have a set of jugs and pistons from my XJ1100 and they are fine and came out of a working, running XJ1100 just before I decided to increase HP with a Wiseco 1196. You would need to check compatibility and then we could talk.

If you need more information, or pics, just say the word.

Thanks
Jamie

 

Heck it might be cheaper finding someone selling the whole motor

 

Got one of those too! LOL

Jamie

 

valve shims where already replaced. that was the first problem. they where to tight and i wasn't getting compression because they weren't closing before compression started. after that i got compression on cylinders 1, 2 & 4. 3 still had problems and turned out to be bad rings.

part interchangeability is the question. i've read a lot of things on here and it seems like a lot of the parts from the same sized engines are just better reinforced on the turbo models but i don't have the xj cd to really check if i can substitute parts between. i've found what is supposed to be a good set of turbo jugs on ebay from someone parting out the bike. i'm getting a lot of suggestions to do things that are already done but no one has answered the question, are the jugs from an 83 xj650 seca turbo interchangeable with my 82 xj 650 maxim non-turbo? or if anyone has a good set of jugs that doesn't need machined from an 82-83 non turbo 650 they are looking to sell, i would definitely be interested in talking to you.

but the bike is at the shop and they are getting itchy to get it out because they have limited space and people are bringing in a lot of bikes to get ready for spring riding. so now i'm getting into a time crunch. they haven't kicked me out yet but if i can't come up with parts soon they want me to get it out of the way.

 

I would stick with a Maxim 650 "block" as I read somewhere that 2 of the studs are somehow different, and you don't need any surprises.

If the "Turbo" parts are stronger, and some are, you don't NEED the extra strength.

Try to pick up a piston, too - then your mechanic will have all the stuff they need to finish the job.

 

A quick check on the part #'s show that the 650 turbo uses a different base gasket, and the 650 turbo cylinders also have an electronic sensor (spark knock?) attached to the front that the maxim does not use.

These differences would be enough to say they will not interchange directly.

With the YICS engine you will be limited to 82-83 cylinders only!

Ghost