Welcome to the forum.

Nice first post. Ask as many questions as you can!

 

You should be able to find the number that starts with a w on a tube under the seat. The first two numbers after the w are the year.

The throttle cable is attached to what’s called the slide which houses the needs and is pushed on by the throttle return spring. The slide opens and closes to reduce and increase airflow and fuel flow which raises rpm. The cable should pop out if you push the cable down through the slide. Gonna have to inspect it because there are different methods of keeping the cable attached.

throttle being stuck open could be an issue with a few things. Open up the box above the thumb throttle to check for rust or debris that could be jamming it up. Make sure the line isn’t full of rust and maybe squirt some wd-40 through it. The inside of the carb looks pretty dirty so that could be causing that slide to not want to come down. Check the condition of your throttle return spring, the big fat one attached to the slide to make sure it’s still pushing hard enough on the slide. Make sure the sides of the slide are clean to make sure it can move freely in the carb.

I would strongly advise against replacing the carb with that chinese knock off. They never work right and I haven’t had great experiences with them.

what’s the problem with the back brakes? Does the handle or foot brake just go all the way down or just the rear caliper doesn’t engage? There should be a bleeder valve on the rear caliper that will look like a little 1/4” nut with a nipple on the end. You depress the brake, open the bleeder valve, close the bleeder valve, then pump up the brakes and repeat to bleed them. Could be dirty fluid or just super worn pads that can’t make contact. Also could be a broken line or seized/leaking caliper.

belt looks ok from where I can see it but I would need a better more in line pic of the belt on there to determine. Also need to have the belt pulled off or again a better pic of the toothed side of the belt to determine if it’s good.

Overall:
rebuild the carb. Plenty of videos and not too hard to do.

clean and general inspection of the throttle cable and thumb throttle assembly

more info on back brakes and belt for a better answer.

Year should be under the seat.

Going to have to kind of figure out the throttle cable but generally you push it through and push it out if whatever’s holding it.

Got all that? 😁

 

You should be able to find the number that starts with a w on a tube under the seat. The first two numbers after the w are the year.

The throttle cable is attached to what’s called the slide which houses the needs and is pushed on by the throttle return spring. The slide opens and closes to reduce and increase airflow and fuel flow which raises rpm. The cable should pop out if you push the cable down through the slide. Gonna have to inspect it because there are different methods of keeping the cable attached.

throttle being stuck open could be an issue with a few things. Open up the box above the thumb throttle to check for rust or debris that could be jamming it up. Make sure the line isn’t full of rust and maybe squirt some wd-40 through it. The inside of the carb looks pretty dirty so that could be causing that slide to not want to come down. Check the condition of your throttle return spring, the big fat one attached to the slide to make sure it’s still pushing hard enough on the slide. Make sure the sides of the slide are clean to make sure it can move freely in the carb.

I would strongly advise against replacing the carb with that chinese knock off. They never work right and I haven’t had great experiences with them.

what’s the problem with the back brakes? Does the handle or foot brake just go all the way down or just the rear caliper doesn’t engage? There should be a bleeder valve on the rear caliper that will look like a little 1/4” nut with a nipple on the end. You depress the brake, open the bleeder valve, close the bleeder valve, then pump up the brakes and repeat to bleed them. Could be dirty fluid or just super worn pads that can’t make contact. Also could be a broken line or seized/leaking caliper.

belt looks ok from where I can see it but I would need a better more in line pic of the belt on there to determine. Also need to have the belt pulled off or again a better pic of the toothed side of the belt to determine if it’s good.

Overall:
rebuild the carb. Plenty of videos and not too hard to do.

clean and general inspection of the throttle cable and thumb throttle assembly

more info on back brakes and belt for a better answer.

Year should be under the seat.

Going to have to kind of figure out the throttle cable but generally you push it through and push it out if whatever’s holding it.

Got all that? 😁

Thanks for all that, really good info!
I cleaned out the carb last night with carb cleaner and managed to actually get her fired up on the first pull! Idles pretty nicely but smells like there might be some bad gas or other debris in the engine. Maybe running will clear it up over time. Here's a before pic of the carb insides.

As for the rear brakes, I can pull the handle brakes and I feel a good bit of tension / pressure, but I can still push the ATV with little force. I assume the pads are just really worn or the fluid is junk.

 

The part number on the seat reveals it is an 85-88 Cylcone, Scrambler or Trail Boss.

The cable attached to the carb in the enrichener cable - unscrew the brass piece threaded into the alloy carb body and you may have to heat the carb to soften the goo holding the plunger in place - I just serviced one of those carbs and had to cut the cable with side cutters to remove the threaded termination of the cable from the brass adapter and then remove the brass adapter. After heating the carb to about 150 degrees I was able to use the inner wire of the cable wrapped around pliers to pull the plunger from the well. After cleaning the carb, polishing the well and plunger, it worked like new again.

You can use the carb you found on Ebay, but really............... For about $100 you can buy a genuine Mikuni carb that will more closely replicate the VM SS carb that was manufactured for Polaris by Mikuni. You can use any damn carb you want to, but it is your responsibility to jet it for proper operation. Just ask yourself, "Where do I get replacement parts for a happy19star carb?" I doubt Mikuni parts will fit it and I'll bet there is not a happy19star distributor near you.

The throttle cable is attached to the slide which you already have removed from the carb, so if the throttle does not return, it's either in the throttle operator or the cable. If it's a Trail Boss (need to find the W number to get the actual model) there were 9 models of TB - 85, 86, 87 and 88 - 2x4 and 4x4 - they were all 250cc - the models were: W867627, W877527, W857527, W867527, W887527, W888127, W878027, W878127 and W878327

 

Thanks for the replies about the brakes and carb, I've serviced them both and have the whole thing back together. The ATV starts and idles really well, but as soon as I open up the throttle it starts to boar horrible to the point where it stalls and can't manage to go up even small inclines. I assume this is because the carb isn't clean enough, so the engine isn't getting enough fuel. What should I do?

 

What should I do?

Completely disassemble the carb especially remove the needle jet (#9) - the needle jet has holes in the sides of it for air coming through the needle jet port at high velocity to mix with the fuel before entering the air passing over the top of the jet which is under the slide and in the center of the venturi. While I do use a heated sonic cleaner that is an advantage over the home shop methods, good results can be had by boiling the carb in water for about 10 to 20 minutes and using 0000 grade steel wool or a brass brush to clean the individual parts. On a severely gummed carb like the one you pictured, it may be necessary to boil it to be able to remove all the parts prior to cleaning. Spray cleaners are only good for removing surface dirt. And you have not revealed how much compression the engine has. If the engine is low on compression it will act just as you describe even if the carb is new. I once had a Suzuki two stroke motorcycle that start first kick and idle perfectly. It would rev fine in neutral, but put it in gear and you could actually push it faster than it would pull itself. I rebuilt the engine and it again ran like new. You might find the engine had low compression as the root cause of poor performance.

 

Did you remove the main and pilot jets to clean them or just spray them while they were in? If the latter you need to remove them and blow them out with compressed air or carb clean.

 

Pretty sure I just sprayed while they were in, I also sprayed carb cleaner in through the air box while it was running, which helped a lot in the short term.

 

Yep, they need to be removed and cleaned. The jets, especially the pilot jet have super tiny holes in the middle of them that let a certain amount of fuel through and the need to be sprayed through.

 

Ah, I remember spraying those through and seeing carb cleaner coming out of the small holes. Does this mean that there could be another reason for the engine bore?

 

I’m telling ya, if you didn’t pull them out the carb didn’t get cleaned well enough. Other reasons could be that not all of the passages are totally clean, the needle and seat did not get cleaned and aren’t allowing enough fuel in, or the needle in the slide is still dirty and not allowing fuel up through the main jet. If spraying carb clean through the throat by means of the airbox like you did helped it run then the engine is running lean meaning there is not enough fuel. If it were me that would instantly tell me the jets were clogged.

 

Thanks for the info, I'll take it out again and try and totally disassemble and clean it.

 

Sounds good. Try and watch this video for a little guidance.

 

Thanks, seems like this guy has an ultrasonic cleaner, which I don't have. Will just using carb cleaner work?

 

I’ve always done it with carb clean and I have a lot of running machines. Shop owners and experts like Latebird will of course recommend an ultrasonic cleaner but they are not needed as long as you strip it down and get it clean.

 

@Scrappy507 - it's an easy mistake to make when you are working on it virtually instead of hands on - it like describing how to adjust valves with screw tappet adjusters and the engine uses shim adjusters - so few people are working on two strokes we forget they are still out there - you are not an idiot, just a dummy like me.

 

Appreciate it!! I’ve actually never owned a two stroke bigger than my couple weedeaters and blower so I don’t get a lot of experience with them.

 

Update time:

So it's been a while but I managed to find time to clean the original carb out and was wondering if I could get some feedback on the overall cleanliness. I don't want to put it all back together if it's still considered dirty .

While I was taking the throttle cable out, I noticed it's quite "frayed" and might snap pretty soon. Does anyone know where I can get a replacement for it? I don't want to get one thats too long or anything.

Here are the pics.

You can see here in this last image, this bit has a hole that goes through it that is compleatly gunked up. What's the best way to clear it out? I've boiled it twice now and used a needle to poke through, but it still seems really clogged.

 

Update time:

So it's been a while but I managed to find time to clean the original carb out and was wondering if I could get some feedback on the overall cleanliness. I don't want to put it all back together if it's still considered dirty .

While I was taking the throttle cable out, I noticed it's quite "frayed" and might snap pretty soon. Does anyone know where I can get a replacement for it? I don't want to get one thats too long or anything.

You can see here in this last image, this bit has a hole that goes through it that is compleatly gunked up. What's the best way to clear it out? I've boiled it twice now and used a needle to poke through, but it still seems really clogged.

Did you ever determine exactly what model you have?
87 Cyclone W877828
87 Trail Boss W877527
87 Trail Boss W878027
87 Trail Boss W878127
87 Trail Boss W878327
88 Trail Boss X888528
88 Trail Boss R/ES W888528 (reverse & electric start)
88 Trail Boss 2x4 W887527
88 Trail Boss 4x4 W888127
89 Trail Boss W898527
89 trail Boss 2x4 W897527
89 Trail boss 4x4 W898127

Carbs are all basically the same, but there were some differences based on the model installed on.

You should simply replace # 18 and 23 - you need to remove #9 (remove washer 19, heat carb to about 200 degrees and push #9 out the top) try soda or walnut shell blasting it clean to be usable or just replace it also. You should soda blast the carb body (inside all the passages) and the inside of the float bowl also, then sonic clean to remove the baking soda from the passages.

Throttle cable is part number is about $160 (depending on the model) or you can package it up, send it to Motion Pro for duplication or replacement of just the bad wire for about $100

 

Swing arm bearing is completely gone

You will need to replace 14, 7,15,16 , 9, 10 and possibly 13 - while you have the swing arm out you might just want to renew the other side also

 

Awesome, thanks for that! Any suggestions on where to look for these parts? I've been using eBay but I'd be interested if you had any alternative places to look

 

Babbits. Find the category that the swing arm is under and you can order straight from there or just get the part number and order it from somewhere else. The numbers from Latebirds diagram and these ones should be the same but double check so you don’t order the wrong thing.

 

Good site, this link seems to be the one for my specific model. Sadly they seem to not have most of the parts I'd need to make the repairs.

 

When it comes to discontinued and NLA parts, it's a choice of Ebay and the phone - you may have to call every Polaris dealer in the US to run down the parts or try to find a good used part from a donor machine. There are salvage yards scattered all over the US and you might just want to try to find a twin to purchase for the parts that are in it. If you are resourceful and determined, you can try to find parts from the source (Polaris does not make bearings or seals) and certain special parts can be duplicated by a machine shop.

I just checked with Polaris and parts 9, 10, 13, 14, 15, 16 are NLA - part #7 is still available

Use caution when ordering from Babbits, Partzilla and other online suppliers - they will take your order, charge your card and then inform you the parts are NLA - this happened to me once and it took 30 days to get a refund

You can use the part numbers they provide to aid your search on Ebay and other sites

I have 8 #14 in my inventory, but that's all that I have - shoulder bolt #32 is still available from Pol - all other parts are discontinued

 

Thanks for the info, I figured it wouldn't be easy getting specific parts for a 33 year old machine, still didn't think they'd be after $14 for a bolt haha. I'll start on eBay messaging some sellers that have clearly stripped down Trail Boss', they might have some of the parts I need.

 

Try powersportsnation.com

 

As an alternative to a whole new throttle assembly, would it be possible to repair the existing wire?

 

If you trust your work anything is possible. I wouldn’t recommend it just because it controls the entire machine but I guess you could.

 

Thinking about it I'm not even sure it's possible, as the cable splits in two and the box where that happens seems to be totally glued shut.

 

Also the machine has an etc or electronic throttle control above the throttle lever that has two contacts that shut and kill spark if the throttle gets stuck. If you fix it you may lose your throttle cable adjustability which that etc system relies on to keep the contacts open and working properly.

 

Oh I see, never actually seen that mechanism. What do you suggest I do?

 

I guess just try and find the cable somewhere or try and find somewhere that can make one. The rear axles on my sportsman 700 are discontinued but I found them at a dealer near me and they gave me a discount on them.

 

BTW the old models did not necessarily have the Throttle Safety Switch - I know the Cyclone did not have it.

 

All of those machines use the same part number so the same cable so yes you should be able to.

 

I'm not sure, from looking at pictures of the cables from the snowmobile list above, a lot of them don't look like they'd really fit. Some even split into three cables. I'm wary of dropping $150 on a cable just to have to send it back and potentially fight with manufacturers / resellers...

 

This cable has been looking like my best bet for a while. Relatively cheap and from Motion Pro. Looking at the images though, the small metal ball on the end that goes into the carb isn't present on my cable. Stuff like that will probably be the difference between it fitting and not fitting. I've also looked on Motion Pro' site, and it doesn't seem like they support my specific ATV either.

 

Finally! Managed to find a sticker on the front of the frame that has a model number on it. I was expecting it to be stamped into the metal. Could barely read it, but I'm pretty sure it's an "W867627"

Currently, I'm looking for a new throttle cable, a new peacock fuel valve, and a whole new swing arm bearing assembly. It's unfortunate that finding the number on the frame hasn't really got me any closer to getting the parts I need haha.


EDIT: I've taken apart the swing arm weldment and it's kinda strange. Nothing looks particularly broken except for these two steel washer things (Could be the bushings, "7555752") although honestly what I'm looking at on the bike looks nothing like the diagrams.

It looks like the previous owner welded a washer to the outside frame, and the bolt simply slipped out of it's housing? I can't really think of another explanation. Images of the parts forthcoming.