Tomos Moped Guides
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[edit] How do I replace the piston and cylinder?
Take off side fairings. Remove airbox with one large philips screw and detach from carburator by unscrewing clamp.
Turn on fuel flow and remove carburator where it attaches to intake with philips screw. Let carburator hang to the side. Unbolt oil injection from intake manifold with one small (size?) bolt.
Unbolt exhaust at bottom of engine and consider completely removing exhaust from moped.
On cylinder head, remove spark plug wire and pull spark plug. Unbolt head from cylinder via 11mm bolts and washer. Wiggle cylinder head completely off engine, pulling it past piston and rings. Stuff paper or cloth in remaining hole to keep debris out of engine.
Unbolt intake manifold from cylinder and remove reed valve. Replace intake and reed valve on new cylinder along with appropriate gaskets.
Remove piston by unclipping 2 retainer rings on wristpin. Slide out wrist pin, tapping if necessary. Remove piston.
Put new rings on new piston by gently working them down over top of piston. Check documentation for ring arrangement. Often, pistons will have a finger in the groove to keep ring alignment at preferred angles.
Slide piston into new cylinder by compressing rings one at a time. Piston should have its windows to the intake side. Scrape old gasket from engine where cylinder mounts and install new gasket. Put new cylinder partially on engine while aligning connecting rod with piston. Slide and clip new wristpin in with needle nose pliers. Slide cylinder completely down onto engine. All this while compressing the rings with your fingers to enter the barrel. Remember the rings (FA type)have to align on the pins in the piston grooves, if not you will break the rings.
Pour a small amount of 2-stroke oil down cylinder to piston. Roll the engine with kickstart or pedals to lube walls of piston and cylinder.
Replace head. Slide washers and nuts on bolts with allen wrench or similar tool. Torque down in X pattern. Be careful not to overtorque. Replace spark plug and wire. 10 foot pounds of torque
Bolt on exhaust, using appropriate gasket. Replace carburator and air box. Turn on gas.
Remember to vary speed while break-in and limit full-throttle operation for 300 miles.
[edit] How do I do a plug chop?
Put in a brand-new spark plug, so you can see the most recent color being deposited. Full warm up the engine by running it for about 10 minutes... Then make a top speed full throttle run for a couple of miles (some say a half-mile is enough, but if you are running lean there will be little deposit to see, especially when using synthetic oils) then kill the motor and stop and pull the spark plug on the spot.
It is important to chop the throttle and turn the engine off with the switch and pull over to stop. You don't want the engine to come to an idle, That will change the plug color. Make sure you look down into the insulator below the end of the threads for the color reading, many fuel additives can give a false color near the tip.
Color guide: No deposits = real lean or you didn't drive long enough. White or grey = lean, you are in danger of damaging your engine. Yellow "glaze" = plug is too hot (e.g. go from B6HS to B7HS). Tan or "light chocolate" = good balance of complete burn, yet not too hot. White tip but insulator brown = lean, but also the plug is too cold (e.g. go from B7HS to B6HS). Red or pink = fuel additive burn-off near the tip, look deeper on the insulator. Brown = a little too rich, slight loss of top end, but good if your conditions vary (load, altitude, temps). Black = too much fuel, you are in danger of fouling the plug.
[edit] How do I replace my chain?
Loosen the tension adjustment tabs at the rear tire by loosening the nut on one side. Tap these until the cams are in the loosest position. Remove the chain guard with two Philips screws. Chain is #415 Find the master link by slowing rotating the rear tire. It will look different than the rest of the links in the chain. Pop it over using a screwdriver and a sharp pop of the wrist.
To avoid needing to pull the left pedal and part of the engine cover, reattach the new chain with the masterlink to the old chain. Keep tension on the chain and slowly rotate the rear tire to pull the new chain forward through the front sprocket.
When the old chain has pulled through, pull the two other parts of the old master link off. Use a new master link to connect the chain.
If you are using different sized sprockets or a universal chain that is longer than stock, you may need to remove extra links. Use a link breaking tool or grind off pins and remove unneeded link sections.
Tighten tension adjustment tabs, making sure to keep them even on each side. Tap with a hammer if necessary. Look for a 10mm deflection in the chain when finished.
Replace chain guard. Use chain lubrication to heavy oil down chain while slowly rotating rear wheel. Considering oiling chain every gas fill-up to lengthen chain life.
[edit] How can I tell if my oil pump is working?
if your bike runs its working but how well is better decided by some one qualified
[edit] How do I add an aftermarket exhaust?
Below the engine at the exhaust outlet are two nuts and washers. Remove these. Another bolt connects the exhaust behind the pedals. Remove this and discard the exhaust. Replace the after-market exhaust, remembering to add an appropriate gasket before tighting bolts and washers. Don't overtorque! You will need to change your jetting at this time also.
[edit] How do I change my rear sprocket? Front sprocket?
Little advice about this. A (27 Tooth) Count will allow for maximum speed to be reached without going crazy with compression issues, jetting, or even boring your ports larger. This is not necessary. A smaller sprocket will allow for a slower top end. your looking at a very cheap alternative, around maybe 15 to 20 bucks US. However if you're not looking to go fast then i would say use a 25 tooth sprocket for the front. Now if you want to go even faster, get a 20 tooth sprocket for the rear. The reason for this is very simple, in the front we have a larger sprocket to create more pull and a smaller one on the back means it completes it rotation faster therefore occupying less space in the back and more in the front will increase the speed of the chains movement. Absolutely the same thing as a bike sprocket the only change here is we are modifying it to be a bit different either faster or slower with more power. The larger sprocket in the rear will give you a much more powerful pull but less speed. A lot less, not a very good idea for road use here. To be safe use the smaller sprocket in the rear and larger in the front :)
Great, but how do I actually change the sprocket?
[edit] How do I plug my oil pump so I can manually add 2-stroke oil?
Remove tank from under seat after you drain off all oil. Disconnect oil lines at tank and under cover where oil pump is. Remove 2 screws from oil pump and put pump aside. Take off coupling insert and put with pump. Now on the intake manifold there is the banjo bolt. remove it with the line from the pump. Get another 5mm bolt and cut off short so it will not stick into the flow of fuel delivery. Insert screw with a fibre washer and tighten so there is no air leaks. Put the old side cover(round) for thepump back on. Double a piece of fuel line to fill in the holes where the oil lines fed in and out. Now mix fuel at 50:1 ratio (as recommended in all Tomos manuals) and you're finished.
If your moped is stock the oil injection may connect directly to the carburetor. If this is the case, you need to plug the hole the oil hose went into originally. The banjo bolt step in the above instructions could also be ignored.
[edit] How do I change my carburetor's jet?
Turn off fuel flow and remove carburetor where it attaches to intake with philips screw.
Invert carburetor and unscrew float bowl. The jet sits in the middle of the float. Be careful not to tear gasket. Unscrew jet and replace jet.
Reverse steps to reinstall.
[edit] How do I change my Oil Injection?
To remove oil injection you will have to plug up the hole in the intake. Then remove the pump found on the left side of the motor under its little cover and block off the hole with sheet metal bolted on.
[edit] How do I fix a flat tire?
Get a couple of hard plastic tire irons at your local bicycle shop. These avoid damage to the rims (especially the chrome ones). Use ONLY proper (motorcycle) tubes. a good idea is to change the inner tube.
