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SOHC/4 Bikes / Re: Superbike bars that fit our wide bar clamps
« Last post by MarshallCS on Today at 01:19:40 AM »
+1, except get the Renthal dirt bike bars with the crossbrace, and then just remove the crossbrace

What is the difference?

Sent from my Nexus 5 using Tapatalk

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SOHC/4 Bikes / Re: Superbike bars that fit our wide bar clamps
« Last post by seanbarney41 on Today at 01:18:49 AM »
+1, except get the Renthal dirt bike bars with the crossbrace, and then just remove the crossbrace
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SOHC/4 Bikes / 79 CB650 - looking for some knowledge/advice/etc.
« Last post by tim0cruz on Today at 01:10:48 AM »
Hey guys – long time reader, first time post-er, you know how it goes… I apologize in advance for the long post, but I’d appreciate any advice you can give, and wanted to give as much info as possible!  Hey, it’s the weekend, right?  Maybe it’s raining where you are…

Intro:
I recently bought a pretty clean 1979 Honda CB650.  It’s my second bike, having recently graduated from a 1981 Honda Twinstar CM200T (fun little bike!).  I was looking for a project – something I take apart and rebuild and get intimate with; and this bike is certainly going to be that .  I need some help/guidance on a few things:
1.   Based on the history, how much of a project am I in for?
2.   How rare are engine parts for the 1979 (and are they compatible with the 1980 model)?
3.   What should be my next course of action?

But first, some pics of the day I got it :D :
IMG_4962 by timmy_boy21, on Flickr

Background:
The PO basically told me he had run it with low oil.  My immediate thought was “seized engine” or “pieces of clutch in the oil pan”, but I actually drained the oil before I bought it and didn’t see any shavings or heavy sediment.
His story was he was riding home and noticed the engine started running “louder” (but no knocking, pinging, metal on metal noises, according to him), so he immediately pulled over and towed it home. Once home he noticed that there was low oil in the bike, so he topped it off, and even started it (but didn’t ride it) 2 times after the incident.  After that, it sat in a garage for ~1 year.

What I’ve done so far:
From what I can tell, the motor turns free (rolls forward in 5th gear; don’t have a big enough socket to turn the crank nut).  I’ve drained the gas, cleaned the carbs, changed the oil and oil filter (that f’in filter bolt…), charged the old battery, and tried to fire it up today, but it didn’t (lights worked though).  I even hooked up the bike to a car via jumper cables, and still no motor turn (I hear a single audible click that sounds like it’s coming from the regulator/rectifier area, but nothing spins, or even sounds like it’s trying to spin (i.e. a struggling starter motor)).

Also, upon close inspection of bike I’ve noticed a couple “weird” things:
a)   WTF is this ugly metal “patch” on the left side of the engine?  Is this a crappy band-aid repair from the PO?  And what would have caused this?  Is case failure common at this point?  I also noticed the PO painted this section of the engine case…wonder what he was covering up?!
IMG_5003 by timmy_boy21, on Flickr
IMG_5002 by timmy_boy21, on Flickr
b)   There is only 1 throttle cable coming from the grip – is this model/year supposed to have 2?
c)   The PO had a strip of duct tape with a skit cut into it covering the air filter (perhaps to compensate for the 4-into-1 exhaust?)
d)   Several random non-OEM fasteners (the carb bowl screws, rubber tank mount, etc)

So back to my questions:
1.   Based on the history, how much of a project am I in for? 
a.   Do you have a diagnosis/estimated guess as to what could be wrong, and/or why it won’t start?
2.   How rare are engine parts for the 1979 (and are they compatible with the 1980 model)? 
a.   I’ve got a lead on a complete engine for ~$200 that suffered a blown head gasket – are parts so rare that it’s worth snatching that up?  Or is that another too risky move?
3.   What should be my next course of action?
a.   I had planned to get it to run, then to completely disassemble down to the frame.  I was planning on rebuilding the motor anyways…should I just go ahead and start with that, or still try to get it running?

Sorry again for the long post – hopefully some of you made it to the end  :wink:.  Let me know your thoughts!
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SOHC/4 Bikes / Re: Honda CB750K4 Throttle Stop Screw
« Last post by HondaMan on Today at 01:05:21 AM »
If your switch housing has the open groove (still) along the inside of the case around the cable-holding portion of the twistgrip where the "cruise screw" installs, you can make a small, flat piece of [spring] steel to lay in there, which Honda originally had. Theirs was folded in half, about 1" long. This spreads the force along a wider section of the twistgrip, and prevents gouging of the nylon parts by the screw tip. Sorry, mine is on the bike, I don't have a picture to share?
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SOHC/4 Bikes / Re: Summer Road Trip! Washington to Colorado and Back
« Last post by HondaMan on Today at 01:00:20 AM »
I suggest using D8EA (NGK) or X24ES-U (ND) sparkplugs when on long Interstate rides with the 550. It will cool it off a bit and make it smoother.
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Banzai, my pennies' worth:
The "F" cams are real late-opening for the intake valves. They also scavenge more than the earlier cams (like K0-K6). This makes for hotter piston crowns.

If the pistons are forged: the hot-start scenario is often this: the bike runs enough to get warmed up a little, not all the way, then shut off for a few minutes (like going to the gas station on the way to work...). Then, the starter stalls when trying to pull it around. Reason: the forged pistons swell slower with heat than the cylinders do, and they also cool off (and shrink) slower. So, the early-run-shutoff situation with these pistons has long been that the piston clearance shrinks as the bike is, say, gassed up a short distance from the cold start, then restarted. This makes for piston skirt drag. After the cylinders and cases are fully hot, the cylinders shrink slower upon shutoff because the cases are raising their heat into the cylinders, and this drag is not so severe. To work around this issue, the forged-piston manufacturers have always recommended almost twice the normal piston clearance in these engines. While this helps alleviate the issue, it does cause short ring life.

If the pistons are cast (not forged) instead, and the compression is higher than about 10:1 CR, the pistons warp a bit until they are fully heated up. This warp results in the skirts dragging more than normal until the cylinders also heat up all the way. So again, if the engine is run a short distance and stopped, then re-started, the piston drag is quite high.

Also, the ping and knock you are experiencing is much more pronounced with the late-opening cam and extra scavenging of the "F" grinds. If you advance the cam, say 5 degrees or so, the earlier opening will increase the low-end torque (in the 3000+ RPM range) and will wet the chamber a little bit more in the low RPM flow ranges, too. This will reduce the ping. I like to use the earlier "K" cams in high-CR engines for this reason: they have the earlier opening at 3-5 degrees BTC for the intake while also having less scavenge because they are "wider" between the intake and exhaust openings. The powerband responds accordingly: the power comes on sooner, lasts over a wider band, than with the "F" cams. It also falls off a little sooner (like 8000 RPM instead of 9000 RPM), but I am not nimble enough in my shifting these days to stay on top of the 9000+ RPM shifts!
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SOHC/4 Bikes / Re: Pods Thread
« Last post by scottly on Today at 12:28:34 AM »
Must have been something like this that James was referring to: ;)
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your having the same kinda problems im having, I have repainted my upper tree and bar clamp 6 times now, the paint just isn't working. tonight i quit, im gonna find a new paint the paint im using is just problem after problem.

for the powder coating i would just wrap some sandpaper around a dowel or use a drum sander and thin it out.. don't use stripper unless you want it all gone.. 

On a second note hang in there it will work out. Just imagine yourself cruising along on a new minty bike. 
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I had a thread going on earlier this year on this very subject of programmable advance.  In it, I described how I was having far more pronounced knocking and pinging.  One of the first things that I tried to do was tinker with the advance.  Retarding it did not reduce the pinging, it merely cut the power and made it run like it was 200lbs overweight.  I got stiffer springs on the advance (off of a Goldwing advance I believe) so full advance was at 4000rpm instead of the factory 2500rpm.  It made no difference in the pinging y
If retarding the initial advance, as well as slowing the rate of advance, had no effect on the pinging, how will you tailor a programmable advance to solve the issue? ??? 
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SOHC/4 Bikes / Re: Pods Thread
« Last post by goldarrow on Today at 12:15:52 AM »
Very very disappointed...
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