spock58

I believe that the top ends for those Honda 400/450's were interchangeable & people were doing the swap for more power. Not sure how to tell the difference in cyl. heads but using the 400 head would provide more compression. You can go to an online Honda parts place to determine what jetting came stock and compare to what is in yours. Another thing to check is the VIN (serial)# to see what model the frame is - maybe the fenders were switched? There are lots of aftermarket parts out there these days so finding out what you have gets tricky.

Not too sure what you mean, it sounded like you've already confirmed that spark was tested ok?

Better do a compression test, it's possible that the camshaft is damaged - seen it recently on a Polaris 500 engine.

I don't believe a puller is needed, just use an impact wrench to get the nut off. You will need a gasket if that cover is removed.

It's likely that the one way bearing that's part of the centrifugal clutch has failed. To check it out the cvt clutches have to be removed first. There is a cover in behind them that gets removed to access the cf clutch system (that runs in engine oil btw).

It is possible that the fuel pump is at fault but not that likely. They only make a couple PSI which assists in bringing gas uphill to the carb when the fuel is low in the tank. When they fail it usually results in a lack of fuel, not too much. What I suggest you try is a simple test: remove the original fuel line at the carb & get a clear hose of the same size. Connect the hose to the carb and fill it with gas. You need to support it vertically and watch the level in that clear hose. If it drops and cannot hold that level, the problem is with the carb - float valve or float itself is bad. Sometimes it takes quite a while for the level to drop but be patient, I've seen many carbs fail this test! Worth a try and it's cheap!!

First thing with flooding that is suspected is the needle & seat - it could be the problem still. Since it was replaced, did you install a new gasket (or o-ring) on the seat? It's important to get the proper size n&s since there are different styles/sizes available; gravity vs. fuel pump fed.

Usually it's a bad pickup coil on Yamaha's that I've worked on, seen it more than once. I'm interested if that's your issue as well.

I agree with this possibility if the carb isn't the problem. Very common with older 2 strokes.

I'd be curious to know what the compression is - did you test it yet? If it's only three years old, does it have lots of hours on it? Your issue may be electrical which also affects fuel system with efi.

I agree that you don't know much until the motor comes apart. That estimate of 33 hours seems excessive - maybe the guy just doesn't want to do the job. The most it would be, I'm guessing is 20 hrs. depending on the condition. Removal of the engine isn't that bad, just some grunt work involved (engines are heavy, even in mid-sized quads). Possibly removing the engine yourself and taking it to someone who's experienced could be considered.

That was a common complaint with those V-twin CanAm's, especially with the 800. The fix was to cover the exhaust with a roll of high temp header wrap. Not ideal, but it helped. Even the factory tech advisors recommended it to dealerships. Of course they wouldn't cover the cost, haha!

I recommend testing the stator first before looking at the ignition module (CDI & coil).

Howdy slarpa in Finland! how is the weather over there? winter coming soon? there is already enough snow up in the mountains near us for snowmobiling!

Depends what you consider "hard" haha! You'll have to remove the plastic body panels & fuel tank usually. The carb shouldn't have to be removed but be careful with the plastic nut that screws into the carb. This is the piece that connects the cable to the plunger inside the carb. Definitely don't want to strip that part. Otherwise it's straight forward as long as there isn't any corrosion involved.

Basically, one clutch is for engagement and the other is for when shifting gears. If it slips, then further inspection is needed but I'd assume you'd be replacing weights and springs if the damage isn't too ugly.

There's a pretty good chance that the dying out problem is a failed fuel pump. Pretty common on those older 420's and not hard to repair. Of course a ticking sound could be many things, an oil change & valve adjustment would need to be done first. As for the steering being welded? Sounds like impact damage, not unless it turns out to be the factory weld?? With the issues that you noticed it does sound like a crap shoot - the price would have to be pretty cheap to consider it.

Before buying any parts it couldn't hurt to check the cam timing. If the cam chain has stretched and jumped a tooth ( or been assembled wrong) then you could have this problem. An engine can have compression and spark but if the timing is off, it won't run or run right. This also applies to a flywheel key that is tweaked which affects ignition timing.

Well, if it is an Ultramatic they use a separate clutch for engagement. When there's something wrong in that system, then it could cause trouble with shifting since the belt could be turning when it's not supposed to. Hope that makes sense.

If you're getting a new winch I'd recommend a Warn with a mount kit meant for the model you have. It will cost more but be worth it in the end.

Yeah, that sounds pretty typical. Once it's broken in and gets the oil changed things should work just fine - hey, it's a Honda, no worries bud!

I believe that your quad has a CVT system (belt drive) that changes gears automatically, as well as a separate (sub)transmission to change from forward to reverse/neutral gears. Is that the system you have & is it a problem going from F-R-N?

I'm in agreement with what was listed above. All important stuff for sure. The airbox & filter should remain stock on utility quads. The CV style carbs they use depend on this design. You cannot just run an air filter that just bolts on the carb with stock jetting - it's a hassle to get them running properly. I'd like to add that the diaphragm on top of the slide on these carbs is important as well. They must seal well or you won't get proper acceleration.

Don't overlook the spark plug boot - wire connection. If in doubt, cut the wire back...

Voltage regulator/rectifier.