XL600R Jetting

[grreatdog]

I am trying to get a nice old 1986 XL600R up to its potential. This is my first ever Honda after 25+ years of riding DP bikes. So I know plenty about wrenching and tuning in general but almost nothing about this bike. I picked up a Supertrapp EAR pipe on eBay. That is the same pipe I ran on my Yamahas since the early '80's, so I know how to jet for it. To start on tuning for the Supertrapp I opened up the airbox and I bought a Dynojet Stage 2 kit.

The problem, at least in my mind it is a problem, is that the Dynojet kit does not come with a pilot jet. The kit says that that they don't want to mess with the idle circuit so they don't include the pilot jet. Well this thing is so cold blooded to start that I DO want to mess with the idle circuit. On my XT's going with a larger pilot jet not only helped starting but it made better power coming off idle and transitioning to where the main jets and needles take over. Very helpful stuff for low speed woods riding.

But before I go off and order some pilot jets, I thought I would see if anyone has experience with the Stage 2 Dynojet kit. If I can get the idle circuit rich enough with the just the airscrew, which I doubt, then I won't try to source any pilot jets. Any thoughts or experience with jetting the idle circuit?

Second question (and bear in mind that I haven't looked at this setup closely or cracked the shop manual so this may be a stupid question) is whether the twin carbs are synched to open together or are they staged like the twin carb setup on my XT? If they are staged has anyone messed with making the second carb start opening sooner? That was a good extra power trick on the XT setup.

I am really looking forward to uncorking this tractor motor and to see what it will do with a bit more punch and a few pounds left in the garage.

[HeadTrauma]

You'll have to list any mods, see what jets you have already and go from there. I've looked and read until my eyes hurt, but tuning dual carb XR600s seems to be a black art. All anyone can say is "try cleaning the carbs".

Also, the carbs are sequential, like a 4bbl carb for a car. You can adjust the second to open sooner or later for different results. Try the XRs Only site's carb section for reference.

[targetdrone]

Dyno Jet kits $uck. Just go to a 130 (large carb) and a 128(small carb) on the mains. Try about 2 1/2 turns on the idle screw. Go from there. You may want to try shimming the stock needles, but it probably won't be necessary. I made the large carb come on just a wee bit sooner.

[grreatdog]

A 130 and 128 are two of the mains that came in the kit so I will be rejetting the mains with those and doing some spark plug reading to get it right. This kit has several mains so I have some adjustment room. The kit came with new needles, E-clips and spacers so I am in business there. Not to mention I have an assortment of thin SS washers left over from rejetting a couple of XT's. Thanks for the info on sequential opening. I know how to work with that. Bringing the second carb on line sooner but not so soon that it bogged was the trick on my XT.

I am surprised that no one has any info on pilot jets. I doubt it makes any difference on an XR, but going richer on the pilot for a street legal bike like an XL usually makes starting easier and more punch off idle. At least the secondary carb isn't some weird semi CV thing linked to a single float bowl like my XT had. The second carb looks identical to first on my XL but I am guessing that it doesn't have an idle circuit.

Time to crack the shop manual and do some home schooling. Having ridden and wrenched nothing but Yamahas since 1982, this is a whole new world for me. Believe it or not, I don't even know anybody that has owned a Honda so I am on my own.

[HeadTrauma]

The second carb looks identical to first on my XL but I am guessing that it doesn't have an idle circuit.

Thats right, but the secondary carb doesnt have a low-speed circuit either.

I just got done tearing my old man's carbs apart for a cleaning he never did and the bike will idle now. I think the pilot jet was clogged, which is what I suspected all along. Now it just needs still bigger jets. 62 pilot and 125 mains with 628cc and a Supertrapp on an '84 XL600 and it still wants fuel.

[grreatdog]

The Dynojet kit I bought starts with a 128 main on the left, leaves the stock main on the right and has a 124 and a 132 as extras. With my airbox cut and the Supertrapp, I suspect the 124 is worthless. Is the 62 pilot stock or oversize? I want to go up one size from stock and would like to have it on the bench when I tear them down. Also, have you tried shimming up the needles? Simple and cheap way to get more fuel.

[HeadTrauma]

The #62 pilot is stock until '86 when it was upgraded to a #65, according to my Clymer manual. I found a #62 today. I forgot, last week I helped him shim the needles .025" with brass shim stock. If I get the right jets tomorrow I may put the needles back to factory.

Just for reference, the main jet was a #118 stock.

[CrackiN]

I wanted to give you an update on the rejetting kit.I did the installation and although it took about 4 hrs, everything seemed to come out great....Bike cranked right up and ran perfect....I installed the 128 jet in the main slot on the left carb and installed the needles with the clip on the first notch on both carbs just like the instructions said....I can't really say that it made a whole lot of difference but it does feel a little more responsive...It definitely didn't hurt the performance and I haven't been able to ride it long enough to see if the rejetting brings the operating temp down....My normal operating temp is 220-250 degF....If you find your bike running any higher than 260 you might want to shut it down and let it cool off..High temp operation will cause your stator to fail and that is expensive to replace....I would like to try some different combinations with the 128 and 132 jets moving the clip on the needles lower to get more gas, but taking the carbs out again is not something I look forward to at all....I was pretty sure that getting the carbs in and out would be the worst part of the rejetting and I was right...If there was an easier way to do it I would try the different combos to see if it would make a diff....The one thing I can tell you if you want to make the bike more fun to ride is to replace the rear sprocket with a 47 tooth sprocket. Takes all of about 30 min....It made a world of difference with mine and I can still run 70+mph with no problem. The thing pulls the front wheel in 1st and 2nd using nothing but throttle....

Happy Holidays and stay warm

Jeff

[grreatdog]

Thanks for the info. You can't rejet with the carbs installed? You should be able to rejet just by pulling the float bowls and do the needles by pulling the carb tops off. I never had to remove the carbs to tinker with my XT. BTW, I have removed the carbs once from my XL for cleaning and I agree that it was quite a PITA.

[targetdrone]

You can't rejet with the carbs installed? You should be able to rejet just by pulling the float bowls and do the needles by pulling the carb tops off.

I had to pull mine the first time, as all the screws were in extremely tight. On subsequent adjustments, I could pull just the bowls.

Taking off the manifold makes removing the carbs much easier.

[gnnova]

You definitely need to go up on the pilot jet. I have a 86 XL600 with a supertrapp and airbox mod and it needed a 68 pilot to accelerate and start correctly. It had a bad flat spot with the stock 62.

[grreatdog]

Thanks, now we are getting somewhere. How do you guys modify your airboxes? On all of my bikes I drill 1/2" holes in the airbox cover under the side cover and then stick air filter foam on the inside of the airbox cover. I figure if I am facing serious water, I can always stick my spare undrilled cover back on it or slap some duct tape over the holes. But the side cover always keeps water out to the point that I have never needed to cover the holes. Except maybe when I lost my XT in 6' of water. But somehow I don't think my airbox mods mattered on that one. ?

[HeadTrauma]

Most people, from what I've seen, just open up the snorkel hole in the top. Most of my airbox is gone because some genious cut a majority of it out, realized the mistake, and then pop riveted aluminum sheet back on. Ugly, but works ok.

[davek18]

I have a 87 XL600 With XR carbs that I adapted the handlebar mounted choke to with stock xl stuff. The advantage to the xr carbs is that the main jet can be changed easily by unscrewing the cover over the jet and grabbing a 6mm wrench. The needles and needle jets are different from the XL also.

I run 125 mains on both carbs for higher altitude trail riding. 4000+ elevation. At lower elevations, my primary riding is at 700-2500 ft, I swap a 130 into one of the carbs. I can tell no difference between installing it in left or right carb, I think it mixes in the cylinder and doesn't care. I usually put it in the left since it is easier. Pilot jets are unchanged, idle mixture set for best idle, approximately 1 1/2 turn out.

The biggest and best modification is to set the carburator linkage so that both carbs open right off idle together. The secondary carb becomes the primary now off idle due to the staggered opening built into the linkage. I have heard of people swapping needles and needle jets to the opposite carbs too. That really woke my bike up, throttle response at lower revs is astounding, I have put a 16t countershaft sprocket on for street riding and still have a hard time keeping the front wheel on the ground in first gear. If anything it seems to loft the wheel easier with the higher gearing.

It takes a little creative bending of linkage and I had to play with the return throttle cable adjustment to get both carbs opening the same but it was worth it. The slow trail riding tractability is also much improved, the tendency to die between thumps at low speed is nil now and throttle response is very predictable, almost like a rheostat controlled electric motor. Idle and starting is also much improved. Yeah the carbs open differently at higher throttle openings now but it is less picky at higher velocities. Top end power is good.

Air box is opened up, backfire screen gone, stock Honda air filter since I found the others dont stop dirt as well, and a Supertrapp with 12 discs.

[davek18]

I have a 87 XL600 With XR carbs that I adapted the handlebar mounted choke to with stock xl stuff. The advantage to the xr carbs is that the main jet can be changed easily by unscrewing the cover over the jet and grabbing a 6mm wrench. The needles and needle jets are different from the XL also.

I run 125 mains on both carbs for higher altitude trail riding. 4000+ elevation. At lower elevations, my primary riding is at 700-2500 ft, I swap a 130 into one of the carbs. I can tell no difference between installing it in left or right carb, I think it mixes in the cylinder and doesn't care. I usually put it in the left since it is easier. Pilot jets are unchanged, idle mixture set for best idle, approximately 1 1/2 turn out.

The biggest and best modification is to set the carburator linkage so that both carbs open right off idle together. The secondary carb becomes the primary now off idle due to the staggered opening built into the linkage. I have heard of people swapping needles and needle jets to the opposite carbs too. That really woke my bike up, throttle response at lower revs is astounding, I have put a 16t countershaft sprocket on for street riding and still have a hard time keeping the front wheel on the ground in first gear. If anything it seems to loft the wheel easier with the higher gearing.

It takes a little creative bending of linkage and I had to play with the return throttle cable adjustment to get both carbs opening the same but it was worth it. The slow trail riding tractability is also much improved, the tendency to die between thumps at low speed is nil now and throttle response is very predictable, almost like a rheostat controlled electric motor. Idle and starting is also much improved. Yeah the carbs open differently at higher throttle openings now but it is less picky at higher velocities. Top end power is good.

Air box is opened up, backfire screen gone, stock Honda air filter since I found the others dont stop dirt as well, and a Supertrapp with 12 discs.

[davek18]

Sorry guys, after i posted my reply and went back to check on it I found it there twice. Some people just cant' get anything right huh? I don't know what I did wrong, but my apologies. What do you expect from a noob anyway?

[HeadTrauma]

Just to make you feel better, I'll point out that this thread is also three years old.

[davek18]

I feel better now, thank god no one reads these old posts or I might really be ashamed. Besides it doesn't matter when your dealing with 20+ year old machines. I seriously thought about replacing my old beater with a new xr650r but I couldn't touch the ground and it couldn't be licensed in Washington. I had an opportunity to ride a 650 several days this summer and loved it until I had to stop. I have now decided to update the 600. I put 97 XR400 forks with .46 springs and damper shim mods and an xr600 rear shock and swingarm and wheel on it, now it handles much better on street and trail both, and I can touch the ground when I stop. I have purchased spare wheels on ebay and shod them with street rubber, so with a quick wheel and gearing change I am ready to rip up pavement. I bet I'm not the only one out there still interested it these old bikes and if I helped anyone out thats great too.

[Motosprtman]

Dave - didja change the pilots jets if so to what? I am also in Washiongton and workin an 86 XL600

[pwrpapa]

I'm doing the same thing with the carbs on my old 83 XL600 right now, I'm glad you brought this thread back from the dead.

Thanks, Pop's

So making the second carb open sooner is better? I read a tech article on XR's only an it said to make the second carb open later for better velocity an to get rid of the flat spot. I'm also running a 62 pilot, an you say a 65 or bigger is better? My bike is all stock with only 2500 miles on it.

I guess I'm going to have to take them back off an do it all over again, damnit. LOL

http://www.xrsonly.com/content/index.php?option=com_content&task=view&id=28&Itemid=294