AIRHEAD VALVE ADJUSTMENT with Pics

I have a 1982 XJ650 with a 5N8 engine. It never ran good at all. I could never turn the choke off. I had a guy across the street perform a compression check with a Mac Tools compression checker. He said Harbor Freight testers are junk. From left to right 150 140 140 140. So it's getting great compression. So what does tight valves have to do with the piece of junk not starting? The valves have to seal to get the compression so what's the deal? I am getting brilliant spark, compression and I know the backwards petcock is working because the only way fuel flows from the tank is when it's on PRI. I seen this in another post about those worthless hitachi carbs. It stated they cause the most problem of the bike. Do they still make those carbs? Because I am going to destroy them. They need to be put out of business. I also noticed the more fuel in the tank the easier it is to start. I am at a lost. I am in my 40's and I have NEVER NEVER NEVER seen a bigger piece of junk as the Yamaha XJ650 is. I think Yamaha should be told by the government to stop making motorcycles as they have no clue how to make them. They should just make musical items as that's what they started the company for. I can't even ride the bike on the roads because it's not inspected. Just because Yamaha couldn't use the standard 17 digit vin. Is there not another kind of carb to use on this bike? You can't tell me that someone hasn't put something else on the bike.

 

This rant about your inability to cope with your 31 year old motorcycle doesn't belong here.

Please start a new thread if you want advice; then take the advice given.

 

Just froze doing this. These are the readings I got. Ex 1 .004 In 1 .004, In. # 2 .004 Ex. 2 .005 or .006. In #3 .003 Ex #3 .005 In #4 .0015 Ex. .005 or .006. I just don't understand how you can have great compression but if your valves are a hair off it won't start. When you look at the difference between .002 and .0015 it's like a piece of paper. I have another engine is there a section on removing a engine?

 

Think about how much room, and velocity, a volume of anything needs in order to fill up a space efficiently. Then adjust your valves. Swapping the engine isn't the correct course of action. A difference of a hairs-breath in thickness is all that's needed to change the flow characteristics of a valve once it's out of adjustment.

 

First off, get some metric feelers, because .004" is actually closer to .10mm than it is to .11mm, which is spec. K-D Tools' pn 2274 is widely available for around $8.

Next, you don't replace the motor because your valves need adjusting. You adjust the valves. Follow the instructions carefully (or read Part Deux if you don't want to invest in the tool) and "read" the shims on the tight valves then order replacements. Replace the shims on the tight ones with shims the next size (or two sizes) smaller as needed to bring them into spec. Once you know what shims are installed, we can help you figure out what shims you need if the process is unclear.

This is XJ engine maintenance STEP #1 in all of the books. Not a reason to replace the motor. (Ya gotta do it every 5000 miles.)

 

New to the site, so hello all. Fitz, this was something I was going to have someone do for me, but this write up is fantastic! Making things a lot easier for a lot of people. I appreciate the time you put in this one for sure!

 

You're more than welcome. If you plan to keep and ride the bike, having somebody do it for you every 5000 miles can get expensive. So it really does pay to learn how to do it yourself. Keep a log book with what shims you install and the clearances, date and mileage. It will make the process easier next time. Once you "monitor" the valves, you can pretty much predict which ones might go out of spec by the next adjustment, and have those shims at the ready making it a one-step process.

 

Man this is gold!!!!

 

Thanks!

You might also appreciate Part Deux: http://xjbikes.com/Forums/viewtopic/t=29209.html

 

Ok I dont get it. I am almost ready to do this. How do I know wich shims to get before disassembling it? I only have the cash for one gasket these things cost 0ver 70 dollars. Is it possible to buy a ful set of shims then resell what i do not use? Also can I get the shims out witute using that custom tool? I am doing this in a 8 hour time window in my carport so I can only disassemble once. I plan on buying the gasket and donuts when I get my taxes.

 

get the gasket and donuts, have them ready. You CAN'T know the shims unless either you or someone else did them before and wrote down what sizes went in.

You HAVE to pull each shim to see what size is stamped on the underside of it. It's on the underside so the cam doesn't wear it right off.

First you check the current clearance, then you pull the shim and check the number, and put the shim back in. Then you do your math and check the chart to determine the correct shim. Do that for all of them. Then you figure out what can swap around, and what few shims you need to get. Then contact me for the shim pool, or buy new from Len. Either way, an hour and you'll know what you need. Then when the shims arrive, swap them out, put on the new gasket and donuts.

You do NOT have to use 'the tool'. You can use zipties. That's my preferred way, and I have TWO of 'the tools'.

If you need help and want to be walked through it, start a conversation with me and I"ll help you through.

Dave Fox

 

thanks dude. I will let you know. I am also considering letting my local shop just handle it. Still haven't decided yet. Basically I will be going out of town at the end of March and may be putting the bike in for shock seal replacement. may have them to valves too while they have it for that week and save me the aggravation of a rushed carport surgery.

 

I bet they don't know what to do. At least make sure you get a sheet showing:
What the original shims were
what the clearances were
what the new shims are

That way you can correct it.

 

I asked a local shop how much for a valve adjustment, the answer was $300! I ended up doing them myself. fortunately for me, I had prior experience with the late '70s water cooled Volkswagens (rabbit, scirocco) from my auto repair days.

FU

 

what shim set on amazon do I purchase? As far as the shop goes they are a very professional shop.http://www.hudsonmotorcycles.net/default.asp very professional and knowledgeable.

 

your way over thinking this pal, take your measurements, read the sizes on the ones you need, put it back together with the ones that's in it now use the old gasket for awhile, when you get all your stuff, change them.
if you read all the shims, maybe you only need one or two, why buy a whole kit.

 

If you'd rather spend a couple hundred buck for a whole shim kit, that's totally up to you. ME?.......I'd rather just swap out the few shims I'll need for only a few $, but do what you want. Who am I to tell you to save your hard-earned money for something else that you might need it for?

dave

 

I will attempt the measure-close-order shim-re-open and replace method. Because yeah, I do not want to buy a whole shim set either. I found this on ebay http://www.ebay.com/itm/Yamaha-XJ-7...pt=UK_Motorcycle_Parts_13&hash=item53fcb537d2 I may get two for good measure. Just need to find the donuts too

 

Chacal has all the parts you'll need. Start a conversation with him. You don't need to order parts from the uk.

 

Get you parts from Chacal.
Have the gasket in hand prior to doing your first measurement / shim thickness documentation.
Chances are really good that when you remove the cover that your existing gasket will not cooperate.
Do not fret!
Mine was a mess - meticulously clean the gasket material from the engine and cover (make sure no debris falls in the engine). Put a thin bead of gasket sealer on the cover side of the gasket and a light film of oil on the engine side.
I have been able to remove my cover multiple times since doing this without damaging the new gasket.