Jump to content

mlcjot

New member, bought an old Sherco

Recommended Posts

Hi folks,

Picked up a 2000 Sherco 290 this evening for a very fair price. I have a Husaberg FE550 for green laning and light enduro, but now it's time to actually learn some skills!

The Sherco runs reasonably well but has a couple of things that need addressing. One thing I'm wondering about is the revs hanging when I blip the throttle. There's so much conflicting advice online about this but the general consensus seems to be that it indicates a lean condition. I assume this means a lean air/fuel mixture, rather than a lean oil/petrol mixture? I'm new to 2 strokes :) With a bit of luck this can be addressed with the carb, and doesn't mean I've got leaky crank seals :( I am going to play with the fuel screw and idle screw to see if they make any difference.

Video here: https://photos.app.goo.gl/yPfrfujwktA5LjQY7

Apart from that, I'm pretty happy. The bike is a beater, but that suits me just fine.

Cheers,
Alex

Share this post


Link to post
Share on other sites

Thanks Nebulous! Are crank seals pressed into the case halves from the inside on these engines, followed by main bearings? Or external?

Hesitating as in it takes 5 seconds for the revs to drop to idle after a blip of the throttle. Were you able to view the video in the link I posted above?

I wasn't planning on changing jets for the time being, more just tweaking the fuel screw and idle. But yes, stripping and cleaning the carb is pretty much the first main port of call, after a go through your list of suggestions. The bike fires up first kick wearing slippers. It's the easiest starting bike I've ever had.

I'll pull the ignition and clutch covers at the weekend and see about replacing the crank seals.

Thanks again! :)

Share this post


Link to post
Share on other sites

Clean the carb properly and insure proper jet sizes. Should be around 38 pilot and 122 main jet. Find a strand of copper wire to pass through the jets for verification. The fuel screw will be out 3.5 turns or so.  Needle one notch below center.

Crank seals are removed from outside, but do not go there as yet.

Edited by copemech
Na

Share this post


Link to post
Share on other sites

Sounds lean. The first thing I would do is turn the mixture screw out a couple of turns and see if it solves the problem. If it's more than 2.5 turns out and you don't see any difference check the jets are the right size as copemech said. The check for air leaks. Start by squirting soapy water around the inlet manifold while it's running.

There are billions of results on the web about steps after that but as you say it runs well so to me it sounds like idle mixture screw.

Share this post


Link to post
Share on other sites

Some bikes ( in 1970's grass-track ) were required to have no tick-over at all, so needed the throttle stop screw to be well unscrewed. (I am not too sure of the current ACU regulations.)   So you could try that to see if the engine goes to idle sooner.    For Trials you can set whatever tick-over speed you require, some riders even adjust it for particular sections.

Get to see what is the correct method of setting your tick-over mixture and speed.  It is usual to adjust the mixture screw for a peak in revs, then back off the throttle stop screw to reduce the revs to whatever you require...  I usually err 1/8 turn on the rich side of peak, to avoid a lean cut when accelerating.

.

Share this post


Link to post
Share on other sites

Hi folks, thanks so much for your superb advice and suggestions. I stripped the carb just now, the inlet fuel filter had some crap in it but nothing major. All passages were clean and clear. Jets are:

Pilot 37, main 270, drain bolt says 110, and the one with the o-ring says either 60 or 80.

Drained the fuel, it looked clean. Going to refill with fresh. The fuel screw was exactly 2 turns out, I have set it back to that and will experiment with it next time I start her up. I didn't remove the reed block but it feels supple and visual inspection yields no cracks or splits. The tank breather is free and clear but the fuel flows pretty slowly out of the tap. Might just be normal though, it certainly flows fast enough for the bike to run. Would old fuel result in the engine running lean?

I popped the ignition cover to have a quick look, the flywheel is enormous! And a bit rusty. Water has got in there at some point.

On an unrelated note, the clutch drags with the lever held in the first time I put it into gear after starting. The clutch drag goes away almost immediately.

How quickly should the revs return to idle after a blip of the throttle? Straight away? I'll keep you updated. If my efforts with the carb don't work, is the next step to pull the flywheel and replace crank seal?

Share this post


Link to post
Share on other sites

Pulled the reed block. The bottom pair have quite a bit of light showing through. The top pair are closed. Is this normal? Cheers

IMG_20180622_221115.jpg

Share this post


Link to post
Share on other sites

Cold stick of the clutch is pretty normal on many trials bikes. As long as it clears quickly, it's not the biggest deal in the world. Try to free it off by putting it into gear and rocking to and fro before starting. If that doesn't work, put the front wheel against something when you first knock it into gear. Read the "clutch mod" thread in the Beta sub-forum.

Share this post


Link to post
Share on other sites
4 hours ago, mlcjot said:

Hi folks, thanks so much for your superb advice and suggestions. I stripped the carb just now, the inlet fuel filter had some crap in it but nothing major. All passages were clean and clear. Jets are:

Pilot 37, main 270, drain bolt says 110, and the one with the o-ring says either 60 or 80.

A 37 pilot is fine. the Main is the one you are calling drain bolt. Needs to be 120 ish.

Drained the fuel, it looked clean. Going to refill with fresh. The fuel screw was exactly 2 turns out, I have set it back to that and will experiment with it next time I start her up. I didn't remove the reed block but it feels supple and visual inspection yields no cracks or splits. The tank breather is free and clear but the fuel flows pretty slowly out of the tap. Might just be normal though, it certainly flows fast enough for the bike to run. Would old fuel result in the engine running lean?

Three or more turns out on the fuel screw. That may be your main issue! The heavy flywheel will take a bit longer to wind down but your is a bit floaty and surging.

I popped the ignition cover to have a quick look, the flywheel is enormous! And a bit rusty. Water has got in there at some point.

Drill a 3mm hole in the bottom so water can exit and vent.

On an unrelated note, the clutch drags with the lever held in the first time I put it into gear after starting. The clutch drag goes away almost immediately.

How quickly should the revs return to idle after a blip of the throttle? Straight away? I'll keep you updated. If my efforts with the carb don't work, is the next step to pull the flywheel and replace crank seal?

Not straight away! Put the reeds back init and leave them alone.

 

  • Thanks 1

Share this post


Link to post
Share on other sites

trapezeartist: Yep I'm not too concerned about the clutch drag! Totally liveable.

Nebulous: The reeds all look fine. I'm not familiar with 2 strokes really, so am unsure if the reeds should always be slightly open, or if this is a fault.

copemech: I'll revisit the fuel screw when I get back to the bike. Good point about the heavy flywheel, makes sense! Should the reeds always be slightly open? For engine idle speed perhaps?

Thanks!

Share this post


Link to post
Share on other sites
5 hours ago, mlcjot said:

trapezeartist: Yep I'm not too concerned about the clutch drag! Totally liveable.

Nebulous: The reeds all look fine. I'm not familiar with 2 strokes really, so am unsure if the reeds should always be slightly open, or if this is a fault.

copemech: I'll revisit the fuel screw when I get back to the bike. Good point about the heavy flywheel, makes sense! Should the reeds always be slightly open? For engine idle speed perhaps?

Thanks!

reeds may not seal perfectly , yet when under backpressure they will !

it needs more fuel, most all dellortos run maxed at 3.5 turns

Share this post


Link to post
Share on other sites

Nebulous: I appreciate your frustration on my account, but really I love the discovery and the learning and I've had so much helpful input since I posted here two days ago. I'm finding the trials community to be very helpful and welcoming! Thank you :) That video suggests that I should replace the reeds, I'll verify correct float height and put it back together for a test run, and then look at ordering some reeds.

copemech: Roger that, I'll be winding out the fuel screw when next starting her up. Thanks!

I found a Spanish website that seems to have old parts in stock, has anyone had any experience with www.endurorecambios.com?

Have a great weekend. The sun is shining in south-west Ireland!

Edited by mlcjot

Share this post


Link to post
Share on other sites

The reed valves should be closed with no gaps that you can see daylight through. Initially remove reed valve and ensure it’s not bent or distorted. Refit carefully to the block. Have you made sure the throttle slide can move freely up and down? By the sound of the engine and the age I would be looking to change those crankcase oil seals anyway, lube the lips of the new ones with either 2T oil or silicon grease sparingly if you will, the seals allow crankcase compression to escape taking with it some of the fuel and air, on revving up and then shutting down the seals allow air to be sucked into the crankcase which lets the engine run too fast for too long back down to idle. While you’re in there you can check the main bearings for excess carbon which does get in and cause frictional losses and eventually failure. From the sound of the engine on the video it is ok 👍 mechanically, but it’s easy to make sweeping statements. By doing the work you will become more confident in the bike and know your way around so if it stops miles from anywhere you may have a chance of fixing it.🙂

Edited by section swept

Share this post


Link to post
Share on other sites
6 hours ago, Nebulous said:

Cool.  Yeah set float height , pull that screw out a little - and get some fresh fuel in there.   At least ride it for the weekend. Old reeds won’t hurt for a while.  Plenty of British suppliers for Sherco bits. 

The bike itself looks in good nick.            Me - I’m still waiting on ebay , for tiny spanners to do my valve-clearances.  The radiator fins are anything but straight - and the last guy set the bike up for foot-deep mud.  The Tony Bou prancing-machine I was expecting is doing it’s best impersonation of a BSA B40 at present.  Definitely sad when you can’t even ride the thing - due to a stupid 50p spanner. Been a week now. The supposedly tried and trusted machine I bought to take down the drive and mess about with on a patch of grass - has turned into a high-maintainance Diva with no economic end in sight.  Started looking at other bikes now - that’s how desperate I’ve got!

What bike is that? 4 stroke I'm guessing. I'm much more familiar with 4 strokes, altho I probably only know enough to be dangerous, not to actually fix anything :-) 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×