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Another oil starved NX650 is kill

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Hi guys

First post on the forum. I have done some looking around and it seems that I am the millionth unhappy customer served a mc-oil starved engine  :rolleyes:

 

So this will both be my introduction post and a rebuild help thread. I got an 88' NX650 a few weeks ago for a decent price, I figured it was the classic dirty carb honestly. 18K miles and looks to be in good shape otherwise. But it seems that PO and PPO where good about ignoring the rattles and screams of pain the engine gave off. So like any good doctor I have taken the engine part and its now fully broken down, bottom and top end. I should add that i know very little about bikes, a decent grease monkey but no real motorcycle experience. I actually got it to run twice for a few seconds before the tear down, so that gave me hope.

 

The cam and rocker arms are completely fugged. The cylinder liner and piston have some markings on them which are mostly located on the rear intake side (not sure what to do with that information). lots of carbon in the cylinder. Tons of residue on the cylinder head, it must of got in the oiling galley which further starved the cam of oil.. making more residue. However the connecting rod doesn't have any up down play, just a little left right. The piston is not broken or dented or anything. The bottom end looks fine, but I was told that looking at the shift forks would be smart. The shifter post was stripped so I will replace that.

So all signs say that i have an engine that ran low on oil during a cruise rather than a hard romp. The PO said it "lost compression" a few days after taking it on a long trip.

 

But I want to know what else I should look at? I assume I should open up the oil pump but im worried about camming out those stupid Philips head screws also im not sure what i would be looking for.

The cam journals have some scoring on them but its not too bad looking (Should i upload pictures for your analysis?). I'm too cheap/broke/stupid to want to buy a new head so I would like to just clean the head and replace the cam. How bad of an idea is that? If they are too bad should i look for a new used head on ebay or get (xrs only, engine dynamics, Millennium tech) to fix mine?

I know i will need to re-bore/hone the cylinder but i don't need any more power, what pistons should i look at? 

The cam chain looked ok, i will figure out how to check that for length, 

 

At minimum my shopping list is: gaskets, rocker arms, cam shaft, re-bore, piston, gear shift spindle, clutch pressure plate nut. What else should i replace?

 

I have the nx650 so i already have the "2nd gear mod" right? What about the 5th gear, do i already have that too? I want to add a kick start but it looks like i can do that later once the engine is back on the bike? 

 

Total newbie that jumped head first into a basket-case bike, help?  :cripple:

I can take pictures of whatever if that will help. 

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Top ends are the weakest link. You may well have no bottom end issues. 5th gear is a Euro FMX650 part. To do the kickstart conversion, you need to install the proper countershaft while you have it apart. You can source the rest of the parts and install them later. The head may be fine and just need a cam and rockers. If you want to go with a performance cam, you may be able to use your cam and rockers as cores (depending on how bad they are) for regrind and hardfacing. Stay away from a Hotcam. They are less expensive, but end up costing more once they fail. If you want to go that route, I'll sell you a lightly charred one that will end up saving you money in the long run. You can put it on a shelf and be mad about the wasted money without having to replace your rockers AGAIN. :foul:  Bore the fugger out, drop in a high comp piston, cam, rockers, valves, gearbox. Done!

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Get a factory service manual and some tools and dig in , take pictures if you haven't done anything like this before, go slowly and ask questions. You'll save yourself enough money to keep plenty of beer in the fridge and the knowledge of being able to do it on any other down the road. Once a person learns this kind of work they can buy more questionable bikes for cheaper, knowing they can rebuild it .

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Top ends are the weakest link. You may well have no bottom end issues. 5th gear is a Euro FMX650 part. To do the kickstart conversion, you need to install the proper countershaft while you have it apart. You can source the rest of the parts and install them later. The head may be fine and just need a cam and rockers. If you want to go with a performance cam, you may be able to use your cam and rockers as cores (depending on how bad they are) for regrind and hardfacing. Stay away from a Hotcam. They are less expensive, but end up costing more once they fail. If you want to go that route, I'll sell you a lightly charred one that will end up saving you money in the long run. You can put it on a shelf and be mad about the wasted money without having to replace your rockers AGAIN. :foul:  Bore the fugger out, drop in a high comp piston, cam, rockers, valves, gearbox. Done!

I will look into the 5th gear, thanks. 

For the kickstart conversion the idler gear is mounted on the right crankcase side right? I will purchase the counter shaft now and do the rest later, but i don't want to miss a part that will cause me to open the entire thing again. 

 

What other cams do you suggest? I was ready to put in my order for a hotcam when i read your post. Buying a used oem stock cam (for more money than the hotcam) seemed like a waste of potential performance.

 

I'm getting the wiesco 101 10.5/1 which seems to be well liked. Will 10.5 be too high to run on regular gas? I'd hate to have a lot of knock because i cant find good gas. 

Edited by Mighty

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I don't want to use hotcam if that means another rebuild down the road. I just want to get the thing going again on a budget. 

 

What are my options?

Having my worn cam and rockers sent out for hardening at web or megacycle seems out of budget. Shopping list total is already getting a bit hard to swallow even without including cam journal fix and a valve job. 

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I would source a stock cam off of eBay before buying a Hotcam. Look for an XR600R or an XRL cam. Or have your existing cam reground by Megacycle, Webcam or another custom cam grinder. Steve has experience with one of them... not sure which.

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I would source a stock cam off of eBay before buying a Hotcam. Look for an XR600R or an XRL cam. Or have your existing cam reground by Megacycle, Webcam or another custom cam grinder. Steve has experience with one of them... not sure which.

Ok thanks, found a stock cam that looks to be in good shape. Will buy it. 

 

Will the 10.5:1 require premium? I'd prefer to be able to run regular just in case. I see weisco makes a 8.7 cr piston. I'll sacrifice power to be able to run bad gas. 

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10.5:1 will likely detonate on the cheap stuff.

That's my thinking. I want to make sure its robust enough to run crap fuel. I lived in central america for a while, there's no way a bike could make it there if it only drank premium.

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That sounds exactly like the poor engine in the XR650L I bought two years ago.  The PO just thrashed the poor thing and let it run low on oil but kept riding it until it stopped running.  Piston, cylinder was shot along with the Rocker arms, cam, output shaft, (no splines left) along with the timing chain, it was really sloppy.  I tore the engine down including splitting the case and did all the gear mods, shifter spring, ect..  Total bill and I did all the assembly work was about $900.00.  I used the stock cam installed the JT 11.0-1 101mm piston and I get no detonation at all.  I rode the bike through Central America last June and it never detonated even on the cheap nasty gas.

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Thats awesome baldy. Where abouts did you ride? I have a soft spot for Belize. I've been to scared to actually do the math on my spending so far. What is the shift spring mod?

 

So here's an update! I got the sucker running! 101mm 8.7:1 wiseco piston, bore/hone cylinder (machinist said it had had worn alot), complete xr600 head/cam/rockers/cover (it was in great condition for the price i paid), 85' xr600 kickstart spindle, 87' xr600 3rd gear half of 5th gear and countershaft, xr500 clutch cover (83' maybe), and 83' xr350r kickstart lever that doesn't fit well. 

 

I also got crf450 forks. I need to figure out how to adapt that. I have read that the xr650l forks swap over but it looks like the xrl have roller bearings while my nx has ball bearings. If the xrl forks can swpa into the nx then i can buy emigs stem kit and press it into the crf triple. I need to do more reading, i'm not clear on how/what needs to be machined on the crf stem in order to make it fit, I might have some access to free lathe work.

 

I also would like to update the rear shock. xr500 or xr250 is what i will likely get, but i'm seriously considering buying a newer cr shock and machining a lower clevis however I think it's too long. Where can I find information on shock lengths from all years and models? If I can find something with an upper eyelet mount thin enough to fit between the nx upper mount, find/chop a spring, and machine my own lower clevis I must have a much wider selection, I just need to find something in the 13.5/340mm range. I want adjustment and i would prefer for the nitrogen bottle to be built into the shock upper don't like the remote hose setups. 

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