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    OEM Valve Guides

    Been trying to put together a set of 1st oversize valve guides for a winter project but there appears to be some confusion on part numbers and dimensions. Anybody know where I can find this information?
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    Valve Guide Question

    Is there an O ring seal between the valve guide and head?
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    Black and White Spark Plug

    Looking for some opinions on these spark plug pics from the right cylinder. Plug is black on the intake valve side and white on the other side. Left plug looks normal but a tad rich. Bike runs great with a fresh bore job, pistons, rings and valve seals. Valve stem to guide clearance was in spec...
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    Cylinder Head Question

    I am thinking about getting another cylinder head off ebay to recondition so I can just do a swap with minimal down time. I always see the cylinder heads sold separately from the cylinder head covers, are these align bored so that a cover needs to stay with a head or are they interchangable?
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    BS38 Choke Plunger

    Anybody have a source for OEM BS38 choke plungers for a '78? I suspect I have intermittent problems with one of them not sealing.
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    Headlight Voltage Drops

    Even though I seldom ride after dark (too many deer in my area) I was looking into increasing the brightness of my headlight on my 78 SE. Currently I have a headlight using a H4 halogen with a 60w/55w Sylvania Siverstar Ultra bulb. I thought I'd start with checking the voltage at the bulb...
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    Boring

    Need to get a set of cylinders bored. Last year I got prices of 40 and 80 a hole from a couple shops. I just got a price from another shop that has new machinery of 375 for 2 holes. I'm curious what others are seeing for the going rates.
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    Low Profile Valve Seals

    Anybody know a source for high quality low profile valve seals that provide extra clearance for a high lift cam? Mike's has them but not sure about the quality of the materials.
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    Cruzinimage Big Bore Pistons

    Does anyone know what the minimum piston clearance and minimum ring end gap specs are for the 78mm pistons they sell? I have a set and there is no paperwork with them at all. Since the pistons appear to be cast wouldn't stock specs be about right possibly allowing a bit for the increased bore size?
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    Transmission Roller Bearing Positioning

    I'm putting one of my engines together and I am hoping someone can answer a question I have long had regarding the positioning of the 2 roller bearings on the transmission shafts. When setting the transmission shafts in the case the roller bearings can be moved back and forth quite a bit, I...
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    Point Housing Gasket and O-Ring

    The gasket and seal kit I have includes a gasket and an o-ring that goes between the point and advance housing and the cylinder head. Is this similar to the tappet adjuster covers in that you use one or the other but not both?
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    Crank End Play

    The crank in one of my engines has some end play, I measured 0.4 mm with a dial indicator. Does anyone know if there is a spec on this? I've looked and looked but no luck.
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    78mm Pistons

    Anybody ever used these? https://www.cruzinimage.net/2017/08/29/74-81-yamaha-xs650-706cc-bigbore-pistons-kit-78mm-447type/ I currently have JE 77.5mm pistons and pretty sure it's time for a rebore and new pistons since they have around 65K miles on them.
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    Rephased Cam

    Was wondering what others have used for a 277 rephased cam. I have a Megacycle rephase in my current engine but that was very pricey, I think around $500 when I got it in 2007. I'm putting together another rephased engine and was wondering what others are using. Was looking at Hugh's service...
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    Cam Timing Question

    Probably been answered somewhere already but how much does the cam timing retard as the cam chain wears?
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    Clutch Drag When Cold

    I have been having some issues with my clutch dragging when cold. Even if I let the bike warm up for several minutes after starting it often stalls the engine when I put it into first. Needless to say this is not so great for the transmission either. I had it apart over the weekend and cleaned...
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    Rod Top Bearing Oil Modification

    650 Central has a service where they drill holes in the pistons from the oil ring groove to the rod top bearing to improve oiling. I have been running JE 700cc pistons in my bike for years and as far as I knew this modification was already present in the pistons from the factory. Am getting...
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    Rod Big End Side Clearance

    I just got my crankshaft back from being rebuilt and was checking clearances, etc. I found that the big end side clearance on one of the rods was under spec. From the info I have the minimum clearance is 0.0059" but I measured it at 0.004" Is this a problem?
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    Crank Rephase Question

    After a crank is rephased is there anything that needs to be done to true the center crank joint? Can the center joint be trued at all since it is a spline?
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    Yet Another Slipping Clutch Thread

    I have found another source of slipping clutches that I haven't found any mention of. I have noticed that the amount of free play in my clutch varies a bit with load and also depends on the gear I am in. If I am cruising in 5th the free play is the same as when I am stopped. Under a load in 4th...
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