TM450

Update... I finally got to ride it for the first time after starting out with a bare frame. I did find out that when the engine is shut off I can definitely hear the centrifugal housing spinning inside. So the clutch bearing even though the kick start works good, it's not keeping the engine from back lashing the starter and gears? It must be weak enough for it to slip only when there is compression kick back.

I'm actually just getting the bike back together and figured it was a good idea to test the engine. Just got the foot pegs back on, so now I can throw the seat on it and see what it does going through the gears. So if it doesn't have engine braking,then it would be the one way bearing on the clutch side that's bad then, and causing the engine to kick back against the starter gears?

I'm sure this has been talked about before. I have a 1987 250 Big Red that starts up great, and runs excellent, but when I shut it off it sounds like the starter gears are clunking. I just rebuilt the engine, had the case split, inspected all the bearings and gears, everything when back together just fine. I removed the starter gear cover to make sure that the flywheel one way bearing was free and it seems to fine when I spin it with no binding, and the starter gears all line up under the cover with the starter. Is it possible for the Centrifugal clutch one way bearing can cause this issue? The kick start seems to be working fine to crank it up to, this is got me stumped. I've read about this happening on other later model Hondas, but it was because the one way bearing was locking up.

Hi AKATV! I have the same problem on my '04 Honda 450s. Where can I find a replacement LCD display? The lens measures 3 3/4"x2" . If I could find one, would it work the same as old display? If possible, is there a way to find out the information stored on the board like the milage and hours? Thank You.

Here's a small update. Been cleaning up the case halves scrapping the old gaskets off and cleaning all the debris out of all the oil passages like three times to make sure it's super clean. When I got to the rear case half, and removed the gears and found a thrust washer down in the bottom that goes on the shift drum along with bit's and peices of what was left a timing chain. There was so much crud and metal in bottom that the filter screen plugged up enough to suck it up out of the grooves that holds it in place.

I found some pictures of the Big Red crankshaft with the new Vesrah rod and crank pin. The first and last picture is with the old crank pin.

Heres something else while rebuilding this engine. Would it be ok to just flush out the oil cooler or be better to get a new one? I know the new ones are a little pricey, but if it's worth it I might just buy a new one.

Yes, the Big Red crank pin hole was fully open on one half, making it easier to press apart. The most critical part is aligning the oil hole, so I just used a yellow marking pin showing where each hole is, that way it makes fairly easy to align. The difference between the Big Red crank and 450 was that the crank pin bores were not drilled all the way through on the 450, and the Big Red was on one half and not the other. I have confidence that this will work just fine after doing one crankshaft. The part that I don't like is using heat near the crank halves when cutting the crank pin in half, even though as you can see where the pin turn blue, i don't think it effected the crank halves, but I still don't like it. The next time I do another one, I'll probably just use a large cutting disc that will pass all the way through.

Thank you jeepwm69. On the other crankshaft for my Big Red when I installed the new crank pin and rod, was to make sure that the cross drilled oil hole in the crank pin was aligned with the oil hole on the crankshaft half that the centrifugal clutch is on. I used a 20 ton press from HF and it has enough force to do the job. When I get the new rod installed and get the side clearance close, then put the crank bearings on and set the assembly on two V-Blocks to rotate the assembly. I then setup a Dial indicator on each end of the crankshaft and rotate it to see how much out of alignment the two crank halves are to each other, then use a brass hammer and smack the counter weight in the direction to bring it closer to align the two halves, this may take a few times to get it, but the closer I get it to specs, the lighter the blows to the counter weight. Also every time the crankshaft is moved, it can also change the rod side clearance. When I done the Big Red crankshaft, I got it in 4 tries, and almost .001" less than what the specs call for on each half. The biggest fear on this particular crankshaft that I see is making a mistake after fully pressing in the crank pin in on the second crank half , because I would run into the same situation when I was removing the old rod and crank pin.

Hello, this is one of my first post on this site. I've been riding Honda atv's most of my life especially 3 wheelers. I found this site interesting because of the tech talk about the Foreman 450s, which I just purchased and other atv's that use the push rod engines.

Ooops! Sorry, I posted in the Sport forum instead of the Utility forum.

Hi all, this is my first post on here. I'm excited to see that there is more technical talk on this site than on other forums. I'm currently working on a 2004 450s that I just bought and it was pretty much clapped out from going under water and mud bogging, so I'm going to revive this machine the best that I can going back with mostly OEM parts that I can. First thing I found was that the piston and cylinder were from Niche and from what I see there sold on eBay made in China. The wear and tear didn't look bad, but the top and mid rings had about a 1/4" end gap which explained the no compression. The PO said it had white smoke coming from the exhaust before it died. I've went ahead and removed the engine from the frame and split the case to clean and inspect everything inside. I wasn't going to do this, but the crank rod had excessive side to side play plus the wrist pin bore allowed to the piston to wobble side to side. I recently rebuilt an 87 250 Big Red and had no problem replacing the rod on the crankshaft with a Vesrah rod kit because the crank pin could be pressed out one side, but this 450s doesn't allow that, so I ended up using a cut off wheel to get the rod off then used a Blue tip wrench to cut the crank pin in half, then I could press the half peices out. The crank pin is made of very hard material, so I don't think my band saw would touch it. Both crank halves cleaned up good. I've ordered a new Vesrah rod kit VA-1017. What other methods are used to replace the rod other than using a blue tip wrench? Here's a couple of pics of the removal.