Exhaust removal of exhaust

Disconnect the pipe from the manifold. Take off the brackets and move the pipe backward far enough to remove and install a new donut.

the exhaust and inlet valves will be moving if you rock the crank back and forward at TDC
this is called valve overlap and indicates that you are timing the valves on the exhaust stoke tdc and not the compression stroke tdc
turn the crank over till you get tdc again and see if the inlet and exhaust valves have clearance and the timing marks line up
timing is done only on no 1 piston TDC position compression stroke

A cylinder efficiency test would be the quick answer. Set the engine to top dead centre on the compression stroke if it is a 4-stroke or any top dead centre if it is two stroke. Lock the crankshaft or engage high gear and apply the brakes to prevent the engine rotating during the test (locking the crank is better). Jam the throttle open and remove the air filter.
Remove the spark plug and fit a commercially available adapter or a modified spark plug which allows compressed air to be fed into the cylinder without leaking.

Once the cylinder is fed with compressed air, leaks through the induction indicates a faulty inlet valve or seat, air escaping through the exhaust indicates similar problems with the exhaust valve or seat and more than the usual dribble of air escaping through the piston ring gaps indicates problems with the piston, rings or cylinder bore.

This type of test is quick and reliable and far superior to wet-and-dry compression testing but the diagnosis is slightly different for a 2-stroke as there are no valves but the process is quite intuitive and a valuable aid to fault finding but stick to low pressure on these engines..

check your timing advance. It may be advanced a little too much. If that is okay, then make sure your spark plug is the proper one and not a sub. Most ATV's use DENSO plugs and these seem to work the best. (Having a spark with a higher heat range will cause the overheat condition). The other thing is your mixture... you may be running a tad rich.. lean it up 1/8 of a turn. Finally, remove the exhaust pipe and see if they is carbon build-up at the exhaust port... lean it over and remove all you can, careful not to allow any to fall into the engine. (Blocking the exhaust will cause a dramatic temperature increase.)

if you are talking about the fuel injection system after installing an exhaust system and fuel management computer its easy. Install all the stock components and remove the fuel management computer. The fuel management computer plugs get plugged back into the fuel injector, throttle body sensor, and factory CDI

Carb is dirty . remove it and clean it with solvent and comp. air . then do a visual inspection on the interior of the fuel tank . sounds like you have aquired some dirt . Good Luck

The VTX 1800 is fuel injected which requires the additional sensors (oxygen, throttle position, etc). However the VTX 1300 is carbureted, which takes the sensors out of the equation. If you are changing the exhaust with a:
Slip on-muffler

• remove old mufflers, and slip on new ones
• could add a better air filter, and you get a better sound, minimal power gain

Full Exhaust System

• Remove old pipes from the cylinder heads (i.e. jugs) and use a rag to wipe off the seat and block the opening.
• once both pipes have been pulled from the jugs, prep your new pipes with windex. Clean them well, finger oil and other gunk can cause bluing spots
• Install the pipes, torque them in place, re-clean the pipes and use a chrome polish.
• Purchase carburetor jetting kit, and either take it to a shop to do it, or you do it. If you have never re-jetted a carburetor before, I suggest you go to a reputable shop and get it done.
• With the carb completed, a new air filter (high flow K&N is what I use - I have gone through the same exhaust system replacement procedure on my sled)

If you replace the exhaust without completing the carb/air cleaner, there is a very high probability that you will get backfires every time you ride. This will happen especially on deceleration, and will eventually blow out your valve seat, causing the engine to feel weak due to lost compression.

It sounds like the camshaft is going flat. The exhaust lobe on the camshaft is the first to wear. Basically the exhaust isn't opening the entire duration it needs to expel the exhaust. This will cause the bogging issue. Polaris uses an overhead camshaft, which fortunately, makes it easier to replace. To check the camshaft:
1. Remove spark plug
2. Remove the large bolt on top of the recoil starter
3. Rotate the engine with the pull rope until the "T" mark on the flywheel is visible through the hole the bolt was removed from
4. Remove 8 screws on valve cover, fuel tank removal is not necessary but gives you more room
5. Remove 4 bolts from rocker arms, lift rocker arms off camshaft
6. Rotate engine again with pull rope to inspect camshaft. The center of the camshaft is the exhaust lobe, intake lobes are on the outsides of cam. The exhaust lobe should be about the same height as the intake lobes, and will be noticeably flat
To replace the camshaft:
1. Remove camshaft gear access cover on right side of engine
2. Rotate engine again until the "T" mark on flywheel is visible, 2 dots on the camshaft gear should be at the top of the gear and will be parallel to the mating surface of the valve cover
3. Locate the chain tensioner, 2 small bolts holding tensioner to cylinder and 1 large bolt in the center. Remove the large center bolt to remove tension. There will be a spring and pin inside tensioner so be careful not to let it fly out.
4. Remove screws holding gear to camshaft, leave the gear on the chain
5. On the left side of the engine, clamp the coolant hose going into the thermostat cover
6. Remove thermostat cover, some coolant will come out but is ok
7. There will be a round cover on left side of engine with 3 screws, remove that cover and pull the camshaft out through that hole.
8. Install new camshaft, make sure the automatic decompression lever does not come out while handling. Keep pressure on decompression lever and hold cam so that the little ball inside the cam is facing downwards, this will help to keep the lever inside the cam
9. Install cover on the left side
10. Install cam gear on camshaft
11. Remove exhaust rocker arm from the shaft and replace with a new exhaust rocker arm
12. Install spring, pin, and bolt in tensioner once the gear is in place
13. Install rocker arms, set valve clearance to .006 in for intake and exhaust
14. Reinstall covers and thermostat cover
15. Option B is to take it to a Polaris dealer to avoid the hassle of trying to do it yourself!
Hope this helps, if you need any more assistance let me know, Daniel

I don't have a trial boss 250 but on most 2stroke engines you should never see the top of the piston through the intake port when the carb is removed as the piston doesn't go low enough, thats by design, its the exhaust side you need to look through to see the piston top(crown), if you remove the exhaust to have a look check the condition of the piston rings while there