• Husqvarna Motorcycles Made In Sweden - About 1988 and older

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1980 WR 390 tips and advice

J

jones390

Husqvarna
AA Class
Hello everyone,

Iv been using this site for along time but this is my first post. Basically im just looking for advice and what ever tips you have for getting this bike to be the best it can be. I guess il start with giving some back ground information. A couple years ago i finally got the funds to be able to get a vintage husky like i have always wanted (i only had a few honda two strokes and a yamaha before). After some searching i was able to find the perfect bike. Its a 1980 wr 390 was a few hours south. It didn't have much information in the add but i took a chance and checked it out. Turns out the owner was a vintage two stroke collector who was getting rid of his huskys to make room for a couple Harley 2 stroke 250s he was just finishing restoring. He had a older 360 that was really rough and the 390 that he had been using as a display bike after do in some cosmetic work to it for about 5 years. The bike ran when i got there but he had trouble starting it and when it was running it idled really high. Just to be safe even with the crazy idle i took it for a quick test drive and it ran great, until the throttle stuck wide open on me and about made my crap my pants while i rode a huge wheelie down the road on what was still technically his bike. once i got the front end down i shut it off quick (it was still wide open) and pushed it back. After some haggling i drove off with it for 1200.

Here it is after i had it for a few months and had started my work on making it better and fixing what ever i could find.

husky1_zps5363718f.jpg



After i got i back i went at the carb and from what i can tell the old owner had just taken a 38 mikuni he had around his shop and stuck it on because it was only for display and wasn't ridden, because the jets that it had in it were all over the place and not one was even close to stock. At that time i had not got to this site yet and from my short search i got a little bit of a idea what i needed (im not really good at jetting) and i ended up pretty close to what the procircuit set up is for the cr390. Im currently running a 6f15 needle (i also have the 6dh3), 470 main, r8 needle jet (i also have the q8) and a 60 pilot (also have a 45), a 2.0 slide and i replaced the cracked rubber manifold that bolts to the reed cage. As it is it runs good but it could be better and about half the time it is a bear to get started. Also i am at 900ft above sealevel.

Since then i have found a lot of information and have a good idea which direction to got but i feel like i want to be sure before i start bringing in more parts. Also i still have a few questions that im having trouble finding information on.

First, what are the important mechanical the differences between the cr/or 390 and the wr 390. In my search i haven't found a real good answer and the majority of the information i have found is for the cr/or and before i use these for references i want to be sure i am not getting things that are model specific. Along with this is there a pdf or a link to a workshop manual for the wr, i have one for the cr/or but i can't seem to find anything for the wr.

Second, how should i do the timing on this bike, i have had no luck finding the set up for doing wr timing or what its specs are only the cr/or and i think that they have different timing from what i have read.

What sprocket set up do you all like best, i dont do a lot of technical riding mostly just two tracks, fire roads, and the occasional hill climb.

What are somethings that i need to check on this bike that tend to be problematical, is there anything i should change on it?

I am going to tear the engine down in a few months and id like to do the 420 conversion because iv read that the 1980 is the only year with a thick enough cylinder wall. But in most threads the people who do them have a cr, which makes me wonder if its the cr head that is thicker is that true. Also if i do it, what other changes need to be made to the bike?

What do you all suggest i go with for my carb set up? I plan on going to a 3.0 slide but im not sure if i should change more and what to switch it to other than maybe go to the exact pro circuit set up, if i do go to the pro circuit set will it work well with my stock pipe?

I have more questions and im sure i will keep coming up with more as i go along but that should do for now. If there is anything you all can think of that i should address or that you have done and liked let me know.

Thank you.

bonus pic for future help.


husky2_zps96d134e4.jpg
 
Do a leak down test on the engine first,before playing with the carb.
WR means wide ratio trans, lighting coil for lights, shorter travel in forks/shocks
Why a 420?, 390's run great and it will only lower the value of it
Frame and engine s/n go to a WR?
Does it have the 3rd tube under the frame?
Looks like a CR?
Others will jump in......
 
Looks to be a low hour 1980 390 WR in good condition.Your engine serial # should begin 2084-xxxx,its located on a tag in the area of the countershaft sprocket cover/right side engine case.You are jetted way too rich,try 40 or 45 pilot,2.5 slide,R2 needle jet,6DH3 needle,with the 470 main you have should be ok.You can try a 3.0 slide with a 35 or 40 pilot,but you will probably have run-on/surging when the throttle is closed after accelerating and want to switch back to the 2.5/40 setup.Pull the cap off the silencer and look at the condition of the packing,and that the core tube in the center hasnt broken off.Ignition timing is 2.0-2.2mm btdc.You are missing the roller wheel/chain tensioner setup on the right side of the swingarm,with the chain set too tight to compensate,running it like that will damage the output shaft and bearing in the trans,Husqvarna-parts.com has all the missing parts available.
 
Jones390,

Like Dave said, that main jet is too rich, but also take into consideration, that a 3.0 slide will give you a leaner condition than a 2.5 or 2.0. That's because the opening is larger & let's in more air when then slide is moving (throttle is opening). So a 470 main maybe ok for 3.0 but not for 2.0 slide. With carburetor tuning don't change too much at one time & write down what your doing, cause it's easy to get messed up.


I'm at almost sea level & my 430 has a 340 main, 2.0 slide , 50 pilot & 1 turn on the air screw, I think needle clip is near the middle. I'm pretty sure my 390 jetting is real close to that too.



The reason the 80 390 where bore able to a 420/430 is because Husky move the cylinder studs farther apart, they already knew they were going to make the 430 in 1981. That makes your cylinder a one year only piece & harder to find (valuable). And yes a 430 cylinder with fit right on your year 390 only.


Like i said i have both a 390 & 430 & if i rode in the woods, i'd take the 390 over the 430 because of the increased torque it has.

The main reason your 390 can be a pain to start is the probably the way your doing it. Husky kickstarter on the big bores barely allow them to turn over fast enough to start vs there 250 brothers. The trick is to prime the cylinder 1st , either by kick it over very slowly a bunch of times , kick it with kill switch depressed, leaning it on it's side or rocking it in gear (3rd) a bunch. Any of these causes fuel to get into the cylinder but it usually won't start because the spark is not there or not there at the right time.

I'd bet your bike starts easier when it hot, because it's already had fuel in the cylinder.

Good luck
Husky John
 
Awesome thank you, i am really not the best at jetting and can get all the advice i can and will try your sujestion. I actually already went through the swing arm and added new chain sliders and a tensioner its just along with a stainless braided throttle cable this spring when i got it out, its just a old picture. Thank you again.
 
And yes its a wr, it has the 3rd bar and the serial numbers match up for the wr. I did a compression test when i first got and it seemed good, what do you think the compression range should be, and is the compression test enough or should i leak test it also. As for the 420 conversion, i most likley wont do it i just am interesed in learning about it.
 
If that was my bike, the only thing I would change is the front forks from the stock 35mm forks to the '81-up 40mm forks. I definitely would not tear down the engine unless is REALLY needs it, and I would not bother with the 420 mod, the 390 has plenty of grunt just as it is. The 420 was just a 430 size bore on a 390, the 10cc difference is the shorter 390 stroke.
 
If you do a leak test, you have a good idea of the crank seals (condition). Pass the test, don't tear it down, ride and enjoy it.
All good tips, 390's are one of the best!
 
I actually have been looking at fork up grades lately, and have thought of that. Id like to go with a moderen front end with disc brakes but i dont wana lose the vintage look or into playing with rake and triple clamp offset, what years did they make the switch to disc upfront?
So i am going to do the leak test but i have never done one on a two stroke bike, what is the process? Also what is considered good for a 390?
Sorry for the dumb questions but with all my other bikes i have had a good manual like the clymers for my model and for the life of me i cant find one for the wr390.
 
'85 was the first year of the disc front. Get any year '81-up 40mm clamps and '85-'88(?) forks and front wheel, its a direct bolt on. Lots of that stuff on eBay.
 
87-88 brakes will only work on a 87-88 fork leg. 87-88 fork leg sets will handle all swede disc brakes, as they came with one older style brake leg and one newer style fork leg..
the 85-86 had a floating rotor and a single piston caliper, the 87-88 had a fixed rotor and dual piston caliper.
the forks were slowly updated, eventually getting a lil more sophisticated damping and teflon bushings instead of bronze..
 
View: http://www.youtube.com/watch?v=cS3aKVXTVbc
/ 2011 Elsinore Grand Prix Vintage Class

In this video you can see for yourself what happens with Pro-Circuit jetting on a 79 390CR.

At 2.00 minutes into the race the rider filming looks over his left shoulder, as my son on the black 390CR Husky #66B, powers by on the outside. At minute 2.48 you can see the trench he dug when he seized wide open in 6th gear.

The Pro-Circuit jetting may work for motocross as the bike ran very crisp and strong. But we discovered later the R-2 needle jet is to small and wasn't letting him get on to the main jet.

We are now running an R-4 needle jet with a 6DH3 needle in the 4th position from the top. Were' also running a 3.0 slide with a 50 pilot and a 480 main jet. The bike seems to start easier with the 50 pilot when cold.

BTW, we were also at about 1000 ft elevation at the Elsinore Grand Prix, but we commonly ride at about 4000 ft elevation with no problem or changes.
 
Ron said:
View: http://www.youtube.com/watch?v=cS3aKVXTVbc
/ 2011 Elsinore Grand Prix Vintage Class

In this video you can see for yourself what happens with Pro-Circuit jetting on a 79 390CR.

At 2.00 minutes into the race the rider filming looks over his left shoulder, as my son on the black 390CR Husky #66B, powers by on the outside. At minute 2.48 you can see the trench he dug when he seized wide open in 6th gear.

The Pro-Circuit jetting may work for motocross as the bike ran very crisp and strong. But we discovered later the R-2 needle jet is to small and wasn't letting him get on to the main jet.

We are now running an R-4 needle jet with a 6DH3 needle in the 4th position from the top. Were' also running a 3.0 slide with a 50 pilot and a 480 main jet. The bike seems to start easier with the 50 pilot when cold.

BTW, we were also at about 1000 ft elevation at the Elsinore Grand Prix, but we commonly ride at about 4000 ft elevation with no problem or changes.
Click to expand...
Ron, Can you explain what you mean when you say "the R-2 needle jet is to small and wasn't letting him get on to the main jet". Are you saying the main jet is not flowing fuel at wide open throttle?
Marty
 
Yes. If the needle jet is too small, it becomes the final restriction to fuel flow and the main jet never comes into play. You can tell when this happens because you can take the main jet completely out and the bike will not "blubber" on the main circuit.
 
Kartwheel68 said:
Yes. If the needle jet is too small, it becomes the final restriction to fuel flow and the main jet never comes into play. You can tell when this happens because you can take the main jet completely out and the bike will not "blubber" on the main circuit.
Click to expand...
OK, Thank you, wasn't sure what Ron was saying there. I understand now.
Marty
 
Sounds like you have other issues that have not been discussed.

If your bike has a WISECO piston, it will need 4-6 thousanths clearance to ride in that type of event. As Dave said, timing needs to be set for the type of riding and rider style for the motor to hold up.

Next check should be air leaks. Get a leakdown tester and test it. You may be pulling air from a bad seal, a small tear in a gasket, a small crack in the carb mount, and other spots.

Check your carbs float level. If it's just a tad low, on a sustained open throttle ride, you will starve the motor just enough to lock it up like in the video. Next is the needle and seat. If the guy you bought the bike from just threw any Mikuni on the bike so it could be on display, it may have a snowmobile carb setting, which has a small inlet needle and seat, for use with a pump. Make sure you have a 3.3mm needle and seat under the floats.

An R-2 is a very large jet, especially with the other jets you list. I think you are possibly band-aiding the real problem with the jetting.
 
I own a few 1980 390's (my favorite bike and displacement of all time). One of them is a George Erl built, 420 conversion. It smokes all of my other 390's. It is the most dependable 390 motor I own as well. Starts on third kick cold every time. Starts first or second kick when warm. Has the broadest, most useable powerband on any Husky I've ridden. I also own a 1980 250 cr and a 1983 500xc that I don't ride because the 420 is so damn good. I can't beat my 500 in a drag race but motocross lap times are much faster on my 390! I don't think you would lose any value doing the 420 conversion, if anything it would be worth more to a post vintage racer! I am currently building another 390 to 420 motor peeking into my Uptite motor to get Georges porting recipe. Again, this motor seems to never need any work done to it. I have tons of track hours on it plus a couple years of racing it and it won't go down. If you have to rebuild a 390 why wouldn't you do the big bore kit?
 
Hey everyone sorry its been so long since i posted but i hadn't had a lot of time to work on the 390 becuase im restoring a old checkmate speedboat and ended up doing a motor swap in my truck so it got put on the back burner for awhile but i finally got all the work done. I went with the carb settings you all suggested, repcked the silencer, added a air filter and swaped changed th oil and put fresh ethonal free gas in that i mixed 32/1. After doing everything the bike is running amazing, it has no issues at any throttle position and will sit and idle until i shut it off. However after taking it for a quick lap to see how it was running i was letting it idle and i noticed a knocking sound coming for the engine, i think in the crank case. I did not notice it when riding so i think its only doing it at idle, i didnt try to see for sure though because i shut it off pretty much as soon as i heard it. I will get it out and start it either tonight or tomorrow to try and narrow down where its coming from and when it does it, also il try and take a video and post it to see what you all think it sounds the most like.
 
When the engine is in neutral with the clutch lever not pulled in the clutch plates can move back and forth inside the clutch basket tabs making a lot of noise. Let it idle and pull the clutch in, I bet the sound goes away.
 
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