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Discussion in 'Thumpers' started by Gregster, Jul 6, 2007.
Can I get a hold of you if I need little things here and there? I am right down the road from you.
Do i need to adjust anything when I take the snorkel out? it sounds little more beefy now
Thanks for that. Will have a look at doing it while the motor is in bits.
Thanks Steve. Another option to look at.
Yeah wondered about that too. Don't matter how big the exit is if the door in is smaller!
You looking for a red, white and blue 86 XL600r tank? If so, I have an 87 that is almost perfect. It was taken off when new by a friend to use an aftermarket tank. Been setting on a shelf for almost 27 years. NO RUST INSIDE. I was going to use it but I found a Red tank to go with red framed bike I'm building. I doubt I will use it. If intereted shoot me a PM and we will work out a price.
Sure man, send me a PM whenever.
So I've been thinking more about how carbs work, since your great explanation, Dave. I do have a few more questions....
Regarding the air mixture screw, this regulates the amount of air that gets mixed in with the fuel in the low/pilot jet, right? So it only applies to idle, right? And I guess the more you screw it in, the leaner the idle mix...
And second question... mostly just our of curiosity.... The bottom of the main jet sits a little lower than the bottom of the pilot jet. Are both of these actually submerged in the float bowl fuel? Or is the main jet submerged and the pilot jet just above the level of the fuel?
Just thinking about it all and trying to understand how it works...
Oh, and also....
Not long after starting to ride my XL600 around, I had the distinct feeling that
A) I want to get better at riding off-road; more confident, more skillful
B) I don't really want to do it on the XL, because it's a bit heavy and also it's so damn beautiful (which is to say that I want to ride something for a while that I don't mind dropping.)
So I started talking to various friends about it (turns out I have a lot of friends around here who ride dirt bikes), and one guy said "Hey, my wife has an NX250 she doesn't want."
I bought it for $250, did a bunch of basic work on it, realized it has a problem with one of it's valves, decided to ignore that problem, got it started, stripped a bunch of plastic parts off it, mounted my old XL600 front fender, and started riding it. And it's fun! Here it is:
I've been posting more technical questions and stuff over in the NX250 thread. I know it's a bit off-topic so I'll leave it at that.
But I gotta say it.... electric start is nice!
Am considering trying to add an oil cooler to my '86 while I have the motor out. Has anyone tried or heard of fitting a later model XR400 cooler? Don't really know the dimensions but read on Thumper Talk of one or two xl600 owners who have done it but gave no real description of how.
Wondering how much cooling it would provide as it don't look very big!:huh
Read about using coolers from JC Whitney etc. but at 11" X 6" X 3/4" might be a mission to fit in.
Interesting discussion maybe?
Pilot jet, screw in richer out leaner, it alters the amount of air not fuel.
If the screw is on the cylinder side of the carb its a fuel screw . In would be leaner. If its on the airbox side its an air screw. Out would be leaner. 2strokes usually have air screws and 4strokes usually have fuel screws.
Regarding the pilot jet/ slow jet, fuel mixture screw and circuit. As you can see there are several names for it but that is not unknown in the mechanical world. The mixture screw can be either an air or fuel mixture screw depending on where it is placed in the idle circuit. Usually if it is in front of the slide, down wind side or nearer the engine it is a fuel screw. if it is ahead of the slide on the air cleaner side it is an air screw. It works on the same principal as the needle jet/main jet where it limits the flow of fuel or air in the idle circuit. It is also a tapered rod that you either retract or push into a fixed orifice by screwing it in or out. Understanding that concept it is easy to see that if it is an air screw, screwing it in richens the mixture by limiting air mixed with the fuel. The opposite is true with a fuel screw obviously.
The pilot jet mainly affects idle, and is adjustable for best idle purposes. There is a little bleed over effect into the low speed range as with any circuit of the carburetor. It takes care of duties when the main circuit is closed down due to the needle for the main circuit and low venturi effect essentially shutting it if. So for a very brief period of throttle opening the slow circuit helps transition to the main circuit as the needle is pulled out of the main jet. There are other factors involved there too such as slide cutaway which is used to promote venturi action for the main circuit, and some carbs have accelerator pumps too (pumper carbs they are commonly called) for the off idle transition.
Both main and slow jets are submerged in fuel all the time, I do not know why the slow jet is shorter officially but I suspect it is to keep it above the flow of the main jet and out of potential crud in the bottom of the float bowl since it is smaller than the main jet and will plug easier. They could in theory put a slow jet in a place where it could use the main jet circuit as a source of fuel drawing though the main jet and metering the mix at idle with the mixture screw. I can see potential transition issues that way so I think they are separate for a good reason. You do see jet sharing sometimes in CV carbs where they use a rubber plug to seal the passage after you put the jet in and it draws it's fuel then through a larger jet but that is a whole different kind of carburetor.
I added an oil cooler, which was a generic aftermarket unit. There are several posts about how and where I added it starting around post #146 (page 10) in my build thread. There is also a bit of discussion about how useful it is; who could benefit from one; who maybe doesn't need one.
Hope it helps a little.
I put an XR400 cooler on my XL600. I had to weld mounts on the steering head to hold it in place, and get a little creative with braided lines and AN fittings but it wasn't too horrible to do as I remember. If you are interested I can send pics and try to revive my memory as to the details. The biggest problem was the choice of fittings and layout, but it worked out once I started mounting things. It seemed impossible to do with the stainless braided lines till I discovered a tool to put the fittings on.
I have a temp dipstick and it seemed to drop my temps about 50 degrees on a hot summer day. There was also the advantage of extra oil capacity provided by the lines and cooler.
Thanks Christian Any help is much appreciated. This project has cost shitloads more than I anticipated (didn't envisiage a rebore etc) so I am looking to make the most of all the info you guys provide in this thread
PS, Just went thru your rebuild Christian Awsome job mate, a man after my own heart although I don't have the same resources
Thanks Dave, Would appreciate that very much. The xr400 cooler is about $96us on partzilla but i'll see if I can maybe get a used one here but am not holding my breath! I read that these bikes tend run pretty hot so any cooling has got to be good and as I replied to Christian this bike owes me big time.
Am having a ball doing the wrenching, just waiting on some gaskets b4 the final assembly.
Well good new after some help from folk on here i manage to track down a new head for my xl600r to replace the one that had been repaired by PO with epoxy and had sprung a leak....shock horror haha.
Well after cleaning it up removing some sheared off studs and grinding the valves in it was all good to go again.....oh yeah new timing chain and stainless exhaust while i was at it too.
Then a few trips out on Salisbury Plain in the wet as we have had loads of rain here in blighty....flooded it once in one of those 'oh thats a bit deeper than i thought moments'.
So all well really the end......yeah right!!
I've started a new job in scotland so got my bike ready to come up.....long distance fuel tank from acrebis. Set off all going well despite being damn cold -7 cold for here anyway. About 50 miles in.....cough....oh what was that hummm. Then nothing so rolled to a stop on the side of the A417. Few things sadder than a bike on the hard shoulder.
So had a look about......oil everywhere. No compression. So from my limited knowledge of these things head gasket? Anyways after a bit of sorting got a lift/flight to work and the bike taken home. New gasket ordered will see how a i get on when i'm next reunited with my bike.
The only thing i can think is that head gasket failed as i refitted the old one (even though it had only done 500 miles) any pearls of wisdom greatly recived. Oh if anyone knows where you can get carb kits (prefereably in the uk) for these wonderful machines that would help too.
Keep it rubber side down,
It has been a long time since I installed it so it is a little fuzzy in my brain but I have refreshed my memory from old notes and observations of the install.
I test fitted for location then welded two 6mm nuts to the side of the oil tank for mounting the cooler. I welded a little shelf underneath it too copying the 400.
I had previously searched many posts and installs myself with hookups ranging from cutting off stock oil lines and using rubber hoses to fabricating new steel lines. I settled on AN fittings and hoses, kind of copying an install I found online using the same. It seemed more leakproof and durable and within my fabricating skills.
First I got the parts:
Oil tank: 16mm female adapter to 6 AN male, and a 45 degree hose end.
Left cooler: 16mm female adapter to 6 AN male, and a 90 degree low profile hose end.
Right cooler: 14mm female adapter to 6 AN male, and a 120 degree hose end.
Crankcase hose: 18mm male adapter to 8 AN male, an 8-6 AN reducer, and a straight hose end.
6’ of 6 AN hose.
Then I started fitting fittings and cutting hose and installing ends and routing hoses and such. I almost gave up the project over the difficulty and bleeding fingers resulting from trying to put AN fittings on the hoses. I discovered a tool, called Koul tool that made the task nearly effortless. I did have to reposition the oil tank breather hose by careful bending and reroute the hose from head to tank.
It took 2 fittings to get from 18mm original hose down to 8 AN, then down to 6 AN, to adapt to the hose and keep the whole thing one size hose.
Then a couple more fittings to adapt to the oil tank, then a short length of hose to the 120 degree and 14mm adapter to get onto the cooler'
The other side of the cooler required a 16mm adapter and a 90 to turn the hose around the front of the steering head and down to the original oil line.
I tried to put the captions under the respective pictures to make the read easier but was unable to comprehend how to do it so you are destined to do some scrolling.