1979 xs650, BBK from yamahaxs650.com, sent rocker box, head, cam out to shop for rebuild/surfacing and porting to match 750 kit. Stock cam, all i wanted was a nice, mild build to putz around on. HHB PMA and capacitor, kick only, mikes xs charge (red) ignition, VM34's from TCBros, everything is new on this build. Spent extra time gapping rings- Top- .008”, second- .010”, oil rails- .008-010”, expander- no gap, skirt clearance was .002-.003". New cam chain with type D tensioner and I guess thats where I'll start with possible questions, new chain is super tight, I dont want to over tighten with tensioner so its backed out a bit from flush for initial start up/testing, if its too tight would that make the engine work harder and get hot? Second question- Are my ring gaps wrong? I got info from here and the actual seller. Third question- I've had issues with the mikes ignitions before. It seems to be firing/working correctly but the pickup is maxed out (advanced) but my timing light is reading just a touch retarded from FIRE mark/ right where it should be. Is my light screwed up? Should i trust this ignition? haha It runs great, except rich bc i'm nervous about this whole deal. What else could be going on? I have oil going to top end BTW. Thank you in advance everyone!
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Running hot after BBK and total top end rebuild.
- Thread starter kwhy3000
- Start date
No one ?
Please tell why you believe it is running hot .
Thinking out loud 750 cc larger capacity more heat .. Oil pump checked ?
Does it shoot in the exhaust because retarded ?
Difficult to start ?
Not rich enough mixture ?
Be careful in running in period ...
Please tell why you believe it is running hot .
Thinking out loud 750 cc larger capacity more heat .. Oil pump checked ?
Does it shoot in the exhaust because retarded ?
Difficult to start ?
Not rich enough mixture ?
Be careful in running in period ...
Last edited:
Thanks for your reply. I have a ‘73 triumph parallel twin 750 that I checked the warmth against. Kind you I am checking with my hand but going to get a laser thermometer soon. Obviously they aren’t t the same engine but I figure similar enough. The XS feels almost twice as hot… too hot… New “high performance” oil pump seems to be working as it should. Running just slightly retarded as per recommendations in this forum. I’ve checked full advance a few times and seems to be on the safe side but I don’t want to rev it too many time because I’m nervous about the temp. I could just keep going richer and see what happens. Starts great; when cold it’s 2-3 kicks, when hot it’s one kick. I dunno…
Maybe I’m being overly cautious bc i have a lot of time/money into it but I really believe it’s running too damn hot.Just thinking out loud here not used them myself but there exists Oil thermometers used in the dipstick hole
Oil cooler is one possibility
Picture of spark plugs maybe.
And yes be careful running in I dont remember those instructions but there is restrictions on revving and so
When I rebuilt I started up gradually Kicking it over many times getting oil everywhere partly because connected ignition wrong When started letting idle for a short while Just warming up
Shutting down ..Letting it cool down And on it again longer times .. Gives the opportunity to feel heat and listen. for noise
It is normal having slightly higher friction in a New rebuild engine and can give a little higher heat rings settle and so
I would look into oil and the laser temp meter and be sure the fuel is rich enough ignition timing right.Consider to advance it a little
just for testing.
Anything known about piston cylinder clearance Is it a set or machined at a local shop I believe a shop measures near the top of the Piston and then the cylinder and machine to the spec which can be different for a 750 set than a 650
Oil cooler is one possibility
Picture of spark plugs maybe.
And yes be careful running in I dont remember those instructions but there is restrictions on revving and so
When I rebuilt I started up gradually Kicking it over many times getting oil everywhere partly because connected ignition wrong When started letting idle for a short while Just warming up
Shutting down ..Letting it cool down And on it again longer times .. Gives the opportunity to feel heat and listen. for noise
It is normal having slightly higher friction in a New rebuild engine and can give a little higher heat rings settle and so
I would look into oil and the laser temp meter and be sure the fuel is rich enough ignition timing right.Consider to advance it a little
just for testing.
Anything known about piston cylinder clearance Is it a set or machined at a local shop I believe a shop measures near the top of the Piston and then the cylinder and machine to the spec which can be different for a 750 set than a 650
This thread might help. Don't think the helpers want to go through this again.
https://www.xs650.com/threads/could-this-make-the-bike-run-hot.64347/page-10#post-800131
https://www.xs650.com/threads/could-this-make-the-bike-run-hot.64347/page-10#post-800131
I had not seen this thread when searching so thank you. I’ll do what I can with this info
AUTOMAN
XS650 Addict
8/10 thou ring gaps?
cliff
cliff
Those are the specs i received from the manufacturer and checked with info on this site as a minimum gap, yes.
