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About deweym21

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    TT Bronze Member

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    Track Days, Touring, Sport Touring, Dirt, Supermoto

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  1. deweym21

    Yz426f: why is compression so low?

    You will not know until you take the valve cover off and check timing. Even if the timing is off, it does not explain the coolant isuse.
  2. deweym21

    Yz426f: why is compression so low?

    Some people, such as myself have installed auto decompression exhaust cams. It sounds like this done probably doesn't have that modification. Again, it would seem to me you have one or more maintenance operations to perform to get the ol' thumper a going again. You're more than welcome to pm me. It seems like you're up for a top end, piston, valve clearance check, new gaskets carb cleaning at minimum. Hopefully the cylinder is still in good shape and not out of round, otherwise you will need to get it reconditioned as well. I would advise getting the entire shim kit and a very good set of calipers or a micrometer to measure the current shims installed so you can calculate the needed shims for each valve and have the correct ones in your stock.
  3. deweym21

    Yz426f: why is compression so low?

    A lot of these bikes are sold with maintenance needing to be done mainly valve clearance checks, top end service, carburator cleaning, ect. One of the main reasons for bikes to lose compression are valves being out of tolerance causing the valve to stay slightly open. if you do not know the history of this bike and perhaps it has a high-compression piston and you're running it on pump gas, then you could have blown the head gasket due to pre detonation. There's a lot that could be happening but as you go through each thing that it could be by the process of elimination then you can get to the bottom of it. I've seen it with my own eyes people riding their four stroke until the valves are out of spec and complaining about it not running and selling it for cheap. That is usually where I start but with your coolant issue it sounds like you need to go a little farther with a top end evaluation and freshening up.
  4. deweym21

    Yz426f: why is compression so low?

    Sounds like you could have a blown head gasket. What is the history of this machine? Have you owned it long? Have you done very much maintenance on it?
  5. deweym21

    2003 YZ450F Kick Starter Shaft Broken

    Have you done a valve adjustment lately?
  6. deweym21

    99 yz 400f

    It sounds like you have a float stuck open in your carburetor bowl from the limited amount of information that you shared. It's probably a good time to take the carburetor off and give it a thorough cleaning and maybe even a rebuild.
  7. deweym21

    Cylinder works/ Vertex High Comp pistion

    They produce a little more power, but the added baggage if needing to run race fuel makes it cost more every time you fill up. They will run on regular fuel (91) but you run the risk of detonation and engine damage. There is plenty of misinformation on this out there. There are products that is supposed to protect against detonation by raising octane which may work. I would buy the real deal to have some confidence in what you are putting in your machine. The increase in power may put additional stress on your engine but maybe that little bit more power is worth it. A lot of people sluff off some of the maintenance intervals and replacement of pistons, but it may be a mistake to neglect it with high compression. If you are searching for more power out of it while the top is off maybe you could splurge on some head work and a real tune by someone qualified.
  8. deweym21

    Rekluse for the yz426f

    If you find something, please reply to this or dm me because i would like to know if i could use it on my SM.
  9. deweym21

    Rekluse for the yz426f

    I think if you search you will find (and may already have) some people have discussed this but nobody confirmed it but there was mention of leaving out some of the clutch plates to make it fit. That is all I know. I hope this is helpful.
  10. deweym21

    Top end rebuild, what happened?

    I wonder if the cylinder service neglected to chamfer the ports after honing. It looks like the rings are grabbing at the ports and scraping the cylinder wall. I'm no 2 smoke expert, but have one that is almost due for a top end and I've been doing some research. Please have mercy, experts, if this is a foolish hypothesis. I hope this is helpful. Good luck.
  11. deweym21

    2006 yz450f backfire issue

    I hate to State the obvious but for some folks you have to. If you do not know much about motorcycles realize this type of motorcycle has an engine that is very high maintenance. One of the most important things that you can do for these engines is valve clearance checks and adjustments other than oil change on schedule. if it's sat for a very long time there could be a carburetor issue. I've seen way too many people ride these until they wouldn't start anymore because of the valve issue. If last valve clearance check is unknown do that or have somebody do that and spend a new spark plug in there and see where that gets you if not your answer is going to be in your carburetor. Or clean your carburetor and do the valve clearance check and spark.
  12. What about your shift shaft seal?
  13. deweym21

    15 yz450 kicking back while starting

    When it starts, does it idle high? granted most of my experience is from carbureted motorcycles and obviously on the four strokes and if you give it throttle while kicking it's going to kick you back so perhaps the idle speed is set too high giving it too much throttle and causing it to kick back on you. I think these fi bikes can give you issue if you have your throttle position sensor off of adjustment. I know this isn't a solution but it's just giving you some things to think about. I hope it's helpful good luck
  14. deweym21

    Yamaha YZ250 (2003)


    After getting my old yz400f, I got used to ripping around with the dirt setup on it before I put some 17s on it for sm, so I scooped up this bike to further expand on my dirt experience. I have ridden it several times at the local mx park and love it!
  15. deweym21

    Yamaha YZ250 2003

    After getting my old yz400f, I got used to ripping around with the dirt setup on it before I put some 17s on it for sm, so I scooped up this bike to further expand on my dirt experience. I have ridden it several times at the local mx park and love it!