So I've had my '93 800 for about 5 years. Bought it from a friend who'd let it sit for a year or so. I've had to do remarkably little maintenance on it. But my friend was no wrencher and I've always wondered, given how much people talk about carbs (I think carbs even had their own section at intruderalert.com!) whether I should fiddle with them, check that they are synced, tuned for elevation (my friend brought the bike to Salt Lake City from Michigan and I wouldn't be surprised if he never redid the carbs for elevation change), etc.? The ONE thing I ever did to the carbs was replace the float on the rear carb b/c it had a pinhole and was taking on fuel. At the time (years ago) I kinda looked into the whole carb adjustment thing but it felt very complicated.
Not sure if backfiring can be carb-related, but I had a bit of it last season, tho it seems to have gone away this season (gosh, I love this bike! It's like it has Logan's healing factor ).
So I wanted y'all's advice. Would a video of how it sounds help determine whether I should start a'fiddlin'?
Popping through the exhaust is often a result of poor sync, with one cylinder dragging the other along. It is not really difficult to do, but is a bit fiddly the first time. Tuning for altitude is basically leaning the engine; as they were rather lean from the factory, you may not need this.
It may also need the valve clearances checked, which can be done while the tank is off to get to the carb sync adjustment.
A finely tuned 800 is optimal.
As WintrSol said, perform a good carb sync and adjust the valves and you are good to go. Both can be a PITA to do.
I adjusted the valves once, and every time I checked them after that they did not need adjustment.
Spec is .003" - .005" cold. Stay closer to .005"
Rejetting is not required.
I tuned my bike for NY State, close to sea level, I've ridden out west to 14000 ft. with no retune.
Thanks, y'all. To clarifying, are you both suggesting a resync and valve clearance check because I mentioned the backfiring, or would you suggest it even if I hadn't mentioned? Because if the backfiring has gone away I'm wondering if you still think I should. Also, I'm surprised that neither of you is pushing for, yeah, doing fiddling on the various jets of the carbs, which I thought is where a lot of people put most of their energy with these things!
Valve clearances should be checked regardless of how the engine is running. Based on your description of your friend's mechanical abilities - you could probably assume they haven't been checked for a long time.
Not sure what the service intervals are for valves on this bike but if you do it now you'll know it will be OK for another 15k miles of so.
Carb syncing is really for the lower end of the carb operation which is where most of your riding is..... so in other words, a proper sync will make your bike a lot sweeter to ride. Again, not something you need to do every 2nd weekend.
The after-fire could have been caused by some junk in the idle passages that has since washed out from use. That said, I'd still do a sync, just to get it running on top, and minimize engine vibrations. Same goes for valves. Once you have it done properly, it will last, and the bike will be that much smoother. I like my engines running top shelf, or as close as I can get.
Followup: If I'm doing a carb sync anyway, shouldn't I clean the carbs up some? Like at least investigate and then take apart and clean deeper to the extent that they look like they need it? I'm not looking for more work but from what little I know about syncing, let's say one carb is dirtier than/not working as well as the other—wouldn't syncing in such a state not be optimal since I'd basically be compensating for a problem I should fix by cleaning?
Also, in terms of tools, I'd like to do this cheaply and I see some on here, esp. lechy, swearing by a simple u tube manometer. Would it be ok to make one myself, and if so, any tips/cautions?
And for the valve adjustment tools, obviously I need a feeler gauge, but do I really need a special tool ("Valve adjust driver" in the service manual) or can I make do with socket wrenches?
The simple U-tube manometer is a great tool, as long as the vacuum isn't so different the fluid is sucked into one carb; using a light oil is usually recommend, so if it is sucked in, no damage is done. If your engine is otherwise running well, I'd say a tank or two treated with a fuel system cleaner, like Seafoam, Techron, etc., should do all the cleaning you need.
I don't have the special tool called out in the service manual; I just used a box end wrench and a very small adjustable wrench.
I have been using a U-tube manometer for many years with great success, even balanced in line 4's with one. the trick is to make sure the connections are leak proof and not drawing air. ATF fluid is easier to see than regular oil. Watch out for the tube and exhaust and be ready to hit the kill switch fast when you first start up.
Here is a guide to valve lash check and adjustment:
Background:
If valve clearances are too tight, the valves can be seriously damaged by warping or burning and compression will eventually suffer from lack of proper valve seating. Valves are cooled by resting against the valve seat if they're open too long, they have insufficient time to rest against their seats and transfer their heat to the cylinder head. On the other hand, if the clearance is too loose, the result will be rough running, loss of power, and excessive wear of the valve train components. Therefore, if you must choose, remember that a little looser is better than tighter.
Before you adjust the valves the engine must be dead cold. In other words, the engine must have been left to cool overnight. The cold clearance is .003 .005 of an inch on all valves. I ended up setting them at .004 all around. However, if you have a bike that tends to overheat, you can set the exhaust to .005 You can also do the opposite, set your intake valves to .005 for better breathing.
Procedure:
If you have a stand or lift, raise the bike; if not, place a 2X4 block of wood under the side stand to prop it up, but make absolutely sure it is firm to avoid having it fall down. I have a small plinth that fits under the battery box.
Remove seats and gas tank.
Remove the front cylinder right hand chrome head cover and take the spark plug out (or just loosen). Remove the rear cylinder left hand chrome head cover and also take the spark plug out (this makes it easier to turn the engine over by hand ). You will be working on the front cylinder valves from the right side of the bike and working on the rear cylinder valves from the left side of the bike.
On the top front and top rear of each cylinder head are the valve covers (four in total). Remove them ([six] 8 mm & [two]10 mm nuts). Make sure you note exactly where and how each cover is placed since they have a thick and thin side. It's a cumbersome process and you will have to loosen the wiring straps (and other stuff) and move around the wiring harness (and other stuff) that runs along the top of the frame to get better access. If your fingers are not so nimble you might have to take out the front carb. The valve covers have rubber O-rings which must be cleaned before reinstall (if the O-rings are flattened or in bad condition, buy new ones). Also, clean the valve covers well and make sure you place the O-ring back in correctly, since it fits in a certain manner. Coat the O-rings with a little oil before reinstall.
On the left engine case cover is a large slotted plug, remove; be very careful since the plug is chrome and sometimes very tight, therefore you can mess it up real easy. This plug has a rubber O-ring which you must cleaned (replace if damaged); smear a little oil before reinstalling. Under that plug is a nut (17 mm) you use to turn the engine crankshaft counter-clockwise. Just in front of this large plug is a smaller plug on the front side of the left engine cover. Remove the smaller plug with an Allen wrench. This is the sight glass used to align your valve timing marks. There is an alignment arrow (a triangle) stamped on the case on the left side of the sight glass looking at it from the front.
Turn the crankshaft counter-clockwise (if you look carefully, the direction arrow is stamped on the flywheel) {also, I turn the engine over a couple of times to take up any slack} until you see on the flywheel (very close to each other) one F/F and one F/T mark (meaning that the front cylinder piston is at top dead center and its exhaust and intake valves are either fully closed or open ). If you keep turning you will reach the R/F and R/T marks (meaning that the rear cylinder piston is at top dead center and its exhaust and intake valves are either fully closed or open). If for some reason you go past the marks, do not turn back, just keep on turning counter-clockwise until you reach them again. Remember that you might have to go several turns because what you are trying to achieve is place the piston at TDC with the valves in the fully closed position, ie: "relaxed". The F/F and R/F marks are for ignition timing (yes, although the ignition is digital, it is timed at the factory). The F/T and R/T marks are for adjusting the valves. Adjust valves at these marks. You will work on the front cylinder first, so get to the F/T mark first. Once the F/T mark is in the center of the sight glass and aligned with the alignment arrow, you must check to see if there is free play at both the intake (on the rear part of the cylinder) and exhaust (on the front part of the cylinder) valve rocker arms by jiggling them up and down. The movement is slight. If not, rotate the crankshaft 360 degrees (counter-clockwise) and check again until the valves reach what I call the "relaxed" position.
Loosen the valve adjuster lock nut (10 mm). It is tight, so be careful not to scrape your knuckles. After the lock nut is loose, hold it with a wrench and work the adjusting bolt back and forth to get the threads in a little easier adjusting shape. You need a special adjuster wrench since the top of the adjuster nut is square. I used needle nose pliers because that's all I had at the time, but buy the wrench.
Insert a feeler gauge between the exhaust valve rocker arm adjuster bolt and the end of the valve. The fit is really tight and you've got to struggle, bend and move the feeler to get it right. Turn the adjuster until you feel a slight drag on the feeler gauge when it is inserted and withdrawn. Close your eyes and feel the slide of the feeler blade to become acquainted with the sensation. If you have a friend who knows how to work a feeler gauge ask him to check it. You should hear and feel a particular rubbing sound as the feeler slides between the metal surfaces. Once you've got it, press the opposite end of the rocker (opposite to where the feeler is) to make sure it's down and you are not getting a false reading (you can also lift the rocker for the same effect). If everything is OK, carefully place a wrench on the adjuster lock nut and on top of that wrench place the special adjuster bolt wrench and tighten the lock nut while holding the adjuster bolt to keep it from moving. Tighten partially, recheck the clearance and if it's right, tighten the lock nut all the way. Recheck clearance. Repeat for the remaining exhaust valve and do the same for the intake valves. (800's have four valves per cylinder).
Now turn the crankshaft counter-clockwise until you reach the R/T mark and repeat the above for the rear cylinder. Make sure you do not go past the mark as the turn will be about 285 degrees. Make sure the valves are in the "relaxed" position.
The biggest hassle when adjusting is being able to slide that straight feeler gauge into a most restricted space, but curving the blade and a few McGyver style moves should do it. If you have never adjusted valves get ready to spend a good while, some cussin' and adjusting several times 'till you get it down pat. Once you have some practice it's faster and easier.
Install the valve, timing and crankshaft covers. Organize your wiring, straps and "other stuff"; Remember to tighten the spark plugs! Replace the cylinder head chrome covers, tank and seats.
RE CHECK THAT YOU HAVE REPLACED BOTH PLUGS ON THE ENGINE COVER
Finally, because you moved the throttle cables around a carb synch will be a good idea.
So it's been a year and I think I'm ready to do this! So the basic procedure for cleaning out the carbs real well is:
- Remove the carbs
- Clean them—should I just spray them with carb cleaner? Or buy the more expensive dip? or what? I should let them soak overnight, right?
- Rebuild—I should plan on replacing all the seals and stuff, right? I saw more comprehensive kits for like $57 but they came with a lot of stuff, and I read elsewhere (I think from Lechy) that I shouldn't need all of it. So I just got this for $10 off eBay. Will that work?
You will need compressed air to blow out the passages in the carbs as well as carb cleaner. You are pretty much wasting your time if you don't do this.
hillsy wrote:You will need compressed air to blow out the passages in the carbs as well as carb cleaner. You are pretty much wasting your time if you don't do this.
Great, was definitely planning on using carb cleaner (see above) and will also add in compressed air to the mix.
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