2005 Sherco ST80 - first ride, maintenance and upgrades.

[diagnosis]

Hello all!  I purchased an ‘05 Sherco 80 last May for $1k Cad. thinking it would be a ‘cheap’ project while I put the majority of my effort into a ‘75 TY175 resto.  I’ve since put a bit more money and a whole lot of effort into sorting some of the cosmetics, and routine maintenance that had been ignored for the past 18 years. 
I was given the option of taking last Friday off, and was cleared of any duties by my wife, so loaded up the bike, and headed North. 
The weather worked in my favour, and was able to get about 50kms in over two rides, along a seasonal access road between my cottage and a nearby town. There are a number of trails and roadside obstacles to play around on along the way, but kept the risk to a minimum being alone, and no cell service. 
I managed to snap a few pics along the way, as the scenery was incredible  
it was a good opportunity to shake the bike down after doing some of the basic seals, bushings and bearings, exhaust repack, brake bleed and new pads, water pump seals, sprockets, chain, etc.  

The excessive smoking finally stopped, the bike felt great, and was surprisingly quick for such a small bore. 

issues that need to be addressed:

- engine noise: I have the replacement main bearings, and gaskets, just need to pull the motor apart and investigate further. 

- front brake is dragging: I’m guessing a rebuild of both caliper and master is in order?

- exhaust popping while riding at a consistent speed: I have no other similar 2 stroke bikes to compare it to, power seems fine, but not sure if this is normal, or maybe a timing issue?

- rear shock leaking: easy fix, take it to Langs for a rebuild  😂 

- 4th gear seems to be missing: I never really had it past third on my street while testing, and  noticed my bike was only a 4sp on the last ride  I’m assuming it’s 4th, as it bogs from 3rd when shifting up, but the final gear seems really long.
Edit: while shifting it manually not running, while on the centre stand, I can shift into 4th, and it won’t engage a gear, just spins as if in neutral. Thinking back, while riding it seems to shift from 3rd completely past 4th into 5th, and down from 5th into 3rd, without hesitation or a false neutral. 🤔 

…. I’ll have to investigate a little further when replacing the mains.  Could this be a bent fork, or detent issue? 

 

Even though it’s had some frustrations, this little Sherco has been a ton of fun and a great learning experience (with a few more lessons to go!) 

🍻

Graham  

How it all began:

 

As of April 21, 2023  

 

Edited May 28, 2023 by diagnosis
Add to to do list.

[faussy]

Looks well! Nothing to really comment on other than the popping is pretty standard for 2 strokes. Thats if im imagining correctly what you are describing, kind of constant throttle on the overrun. I wouldnt worry about it, so long as its clean when under load. On all trials bikes theres always a large jump in gearing between 3rd and 4th, as 1-3 are the section gears and 4,5 are the trail gears. Therefore I wouldnt assume youre missing 4th just because theres a big jump there. 3rd to 5th would be an even more significant jump. 4th gear is probably the most ideal for lane riding, so if it becomes an issue you can always take the bacon slicer off the rear and gear up 1-3 since youre mostly trail riding. Great to see that era of bike still being used.

PS run your eye over your rear brake disc. Those years they had really thin arms and were prone to cracking

Edited April 25, 2023 by faussy

[diagnosis]

Thanks for the reply Faussy, that’s exactly what I’m experiencing with the popping, and glad to hear I shouldn’t be too concerned.  I’ll see if I can figure out the shifting issue either way, but is completely rideable as is.  I’ll try to document anything I do find and post it here for future reference, as it would be nice to give back to the forum, as it’s helped me out a lot so far. 
Also, thanks for the heads up with the rear disc. I realized I was dragging my rear brake caused by poor foot position, and it discoloured from the excess heat.  I’ll take a good look at it, and replace if necessary.

I really appreciate the feedback! 🍻 

[diagnosis]

I had a chance to play around with the Sherco in the parking lot behind my shop this week, and was able to cycle through all 5 gears, but it takes the most delicate touch for it to shift into 4th without skipping past into 5th.   From searching and reading through other posts available on shifting issues, I'm leaning towards a bad or weak index spring? I placed an order through SplatShop, and added a new index, gear selector and return spring, as well as the index roller to the list.  When it all arrives, I plan on replacing the whole lot when I do the main bearings.

Another task this week was cleaning the carb thoroughly, and replaced the carb seals with a genuine Dellorto kit, and plastic cap. The choke tube and choke o-rings were both dried out and cracked, and the o-rings from the Idle and Mixing screw were missing.  As well as the carb issues, the original Domino throttle tube was cracked, and missing half of the top cap, so replaced that as well, along with a new Apico cable, to replace the kinked OG...... I think there was an improvement in how it ran afterwards, but it may just be me, justifying all the work and money going into this bike.  lol!

I tried addressing the front brake drag with an attempt at removing the caliper, and popping out the pistons... unsuccessfully.  I tried compressed air, working them out with a socket inside the hollow of the piston, and rebleeding to pop them out with brake fluid..... I eventually gave up, pressed them all the way in with a vise and blocks, and put them back on the bike.  Re-bled them again, and now they work perfectly.... hopefully they stay this way for a while, but plan on ordering a rebuild kit for when they inevitably p*** fluid all over my new pads!  

Are there any tricks or tools available to aid in pulling the old 4 pot AJP pistons?  

 Hopefully there won't be any more surprises, but I need to remember this bike is close to 20 years old, and this is probably some of the first routine maintenance it's ever received. It's amazing it still works as well as it does!

[turbofurball]

Can you see what's stopping the pistons from coming out?  Is the caliper oxidised or something?  They're simple cups so if they move enough to apply the bakes they should just continue to come out when under pressure ... you might be in line for changing the caliper TBH 😕

[diagnosis]

The caliper seems to be in good shape, and the exposed piston (2mm or so) looks to be in good condition, and there isn’t any noticeable damage or corrosion.  Kinda stumped as to why they wouldn’t pop  under air pressure.  

[tony27]

Haven't done a 4 pot caliper rebuild in a long time so I can't help with why the pistons didn't come out.

I had dragging issues on both ends of my Jarvis replica which is basically a pre-production 05 bike last year, got to the point on the gravel road taking the shortcut back on a trials only trailride that pulling in the clutch going downhill had the bike slowly stopping. Was fully expecting to need to rebuild the front caliper & ordered a kit before having a good look, turned out the problem was well worn pads which I replaced after cleaning the exposed parts of the pistons & pushing them back, haven't had a problem since

A couple of small improvements I'd suggest for your bike are the race/short gear lever, allows removal of the ignition cover without needing to remove the lever & is also tucked in a bit better, the other is to get the later ignition cover that doesn't have the sprocket cover built in, the type you have warp at the back allowing water etc to be flung into the ignition by the chain, the very outside edge needs to be cut back so it sits properly on the case 

Ignition cover part number is 1982

Gear lever part number is 1981 or RQF do their own version in multiple colours for roughly half the price of the genuine piece

[diagnosis]

Hi Tony, thanks for the reply!

I dug into the front brake a little more this week, as I received a new hose to replace the old linked line. There is very minor seepage around the pistons, so will have to get a kit anyways. The old pads were completely worn out and whatever material was left had been saturated with fork oil from blown seals. The pads that are currently on there are $5 AliExpress specials, that are a stand-in until I managed to figure out all the leaks. The last thing I wanted to do was put a brand new set of Galfers in, only to drown in a bath of brake fluid.  I’ll order the kit this week, along with a reputable set of pads.  

I replaced the ignition cover with a newer Sherco model, after trimming, it did fit quite well. I added the oem chain ‘guard’ that screws into the chain guide as well. The old integrated guard was like a proper ‘Cup’ where this thing adds about as much protection as a ‘G-string’.  
I’ll take a look at the shorter lever that you mentioned. It would be so much easier for timing changes and checking for moisture without trying to fiddle around with the lever pinch bolt, and removing the chain. 

🍻 

[tony27]

Good to hear it fits as well as mine does, originally I didn't trim it but had to stretch it over the cases which caused the edge to split beside the wiring. I also have the small piece that covers the rear of the front sprocket fitted

Try fitting the worn out pads to pump out the pistons a bit more then remove & pump some more, the kits come with new pistons & seals so don't worry about marking the pistons once you've split the caliper. When you reassemble with all the new parts in the kit it helps to put some brake fluid in the bore before fitting the pistons & pushing them fully in, helps to make sure all trapped air is pushed out which helps when you come to bleeding the brakes later on

Fork seals are easy to do on this generation bike, it's worth pulling the sliders off & checking the condition of the bushes while you're working on them as the top bush does a certain amount of work keeping the oil in. The lower bush should be consistently black on the outside, the top bush should be copper on the outside & black on the inside

[diagnosis]

Tony, thanks again for the informative reply, I appreciate the advice, and will try that trick to push the pistons out as far as possible.  I received the latest SplatShop order yesterday, so now have all the parts for the front brake rebuild, digging into the bottom end, plus some cosmetic upgrades to appease the instant satisfaction department. 

I plan to split the bottom case to replace the main bearings, and give everything a once over.  There is a bit of metallic debris in the gear oil, not sure if it would be clutch, bearing, or something else, so hoping to sort that mystery out.  For reassembly, should I use some sealant along with the gasket between the two halves, something like Hylomar spray?

 

[tony27]

Just wipe some clean oil on the gasket. Make sure if you do main bearings that you fit Viton seals, splatshop can supply them along with everything else

Last oil change I did after having my cylinder plated I had a bit of bronze appear in the oil, I had the drain washer split so I lost some oil & ran it for 1 ride with less oil than I should have, hoping it was from the inside of the kickstart idle gear rather than the gearbox itself

I'm doing a bit of a cosmetic tidy up myself, headlight surround collapsed & the front guard has some white stress marks in the blue plastic. When I get home from holiday in Europe & the UK I'll have to send the surround & an old rear guard off to have the graphics copied due to unavailability

[diagnosis]

Perfect, thanks Tony!  I did replace the seals earlier this year, but have a set of the Viton seals as well, which will be installed when I finally get to it.  Looking forward to seeing the progress on your restoration when you have time! If I remember correctly, the decals came from MBX Graphics in the UK (I’ll double check my emails if you’re interested), and they were a good replacement for the missing and mangled decals on mine. 
I picked up a new 185mm NG front brake disk (labeled GasGas, but identical to the Sherco), to replace the worn 173mm front disc originally fitted to the ST80, with the 33mm front forks. There didn’t seem to be any options for this size, and the new disc was cheap enough to take the risk to try and make it work.  

Pic below of the old disc over the new.

I’ve had an old manual milling machine collecting dust at my shop that was inherited by my partner.  It needed a plug and some minor repairs, so once sorted decided this was the perfect project to learn the basics.  I designed and 3D printed a mock-up of the bracket, to test fit the caliper and make sure the dimensions worked, then used that print to base the aluminum bracket on, as seen below.

Milling the aluminum adapter was like a dangerous version of etch-a-sketch, but it somehow worked out exactly as planned  over all I moved the caliper 6mm further out from the existing location  It works quite well, but I’m sure once the caliper and master has been rebuilt, along with a new brake hose with the appropriate banjo angle, it will be more brake than I’ll ever need!  

 

Thanks for reading, and have a great weekend!  🍻 

 

 

 

Edited June 4, 2023 by diagnosis