Tappets are way easier, you won't have a problem. Finding TDC compression isn't hard either. Select top gear, rotate the back wheel forward until you see the exhaust valves open and close. Keep going til the inlets open and close, then put a drinking straw or a pen in the spark plug hole and rotate the back wheel until the straw rises to it's highest point. If you miss it and the straw starts to go back down, no biggie. You can rotate the wheel backwards to bring the straw back to the highest point but generally I just go around again.
Edit: once you've found TDC you generally don't need to do anything to lock the crank in place. You can if you want, but nothing is gonna move really. The crank will stay in that position, it isn't under any strain to find a different position.
Refer to my earlier post on page 1 for the puller-size. Very common size anyway. If the crankshaft has any waggle on it - then it isn’t worth putting new seals in until the bearings are done as well. Hopefully it will be ok though. Pay attention to that little woodruff-key - don’t lose it!
Thanks again Nebulous for your help! Your 4t sounds like a bit of a pain. Are the valves shim under bucket type? Or tappets with lock nuts?
I noticed that the Sherco guide says to run 80:1 two stroke mix. Im not one to go against manufacturer's instructions but would have thought it would be more like 50:1. What do you all run? Thanks
You may find that with the crankshaft nut released and a bit of gentle wiggling and inertia persuasion that the flywheel may come lose. The best method though is to use the correct tool. I don’t know the thread size but I’m sure you can get a puller for about £10-15 which is a good investment.
I have a few sizes so will see how I get on. Probably have to buy one though!
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. 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.?
Cool, I'll order some new reeds. There is quite a bit of light showing through. Then, if still no joy, I'll address the crank seals. Do you know what thread pitch I need for the flywheel puller?
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 :-)
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!
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?
I introduced myself over in the Introductions forum but just thought I'd say hi here as well. I picked up a 2000 Sherco 290 yesterday evening for a very fair price and I'm looking to address a possible air leak. You can find some details and pictures/video in this thread if you are so inclined!
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?
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.
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.
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.
I am going to play with the fuel screw and idle screw to see if they make any difference.
New member, bought an old Sherco
in Introduce Yourself
Posted · Edited by mlcjot
Thank you both!
Tappets are way easier, you won't have a problem. Finding TDC compression isn't hard either. Select top gear, rotate the back wheel forward until you see the exhaust valves open and close. Keep going til the inlets open and close, then put a drinking straw or a pen in the spark plug hole and rotate the back wheel until the straw rises to it's highest point. If you miss it and the straw starts to go back down, no biggie. You can rotate the wheel backwards to bring the straw back to the highest point but generally I just go around again.
Edit: once you've found TDC you generally don't need to do anything to lock the crank in place. You can if you want, but nothing is gonna move really. The crank will stay in that position, it isn't under any strain to find a different position.