Need some help please

Hi all,

I have been reading posts from others with issues similar to mine and they have been very helpful. I wanted to start my own to see if someone could answer some questions. I am a computer savvy person, but no previous engine work.

I have a 1982 Yamaha Maxim 650 that we inherited when my wifes father passed a couple years ago. This bike was his daily rider, however, I always saw it ran hard when he rode it, didnt idle well. So I decided to "fix" it. I removed that carbs and attempted to clean them. It needed a cleaning for sure, but some jets werent coming out and others stripped when I tried. So I ordered a whole carb repair kit.... jets, bowl gasket, needle, ect. I recently installed all that and re-cleaned every nook and cranny of that carb. I think I set the 'pilot "air"' screw right, 2 3/4 out, but i cant be sure. I then did a dry and wet float set, they were all too low... but now are good. Installed a new battery as well. I then did a compression test. All were between 90 and 110. So I put some oil, probably too much, into the spark plug hole and the compression instantly jumped 50 or so... so all showed about 140-160. This made me know that the compression loss is probably the piston rings. I then started the bike with the "new" compression readings, fired right up I was really surprised because this thing has not been able to start very well or at all until I got that compression up. Of course it smoked like a SOB, too much oil. It idled high at first, no choke, 3000rpm maybe, but then settled down and stalled. When I tried to give it throttle it bogged right out, even just a little throttle. I drained the oil because it needs a oil change, and filter. It is now sitting in the garage awaiting new oil.

I need to know if I get measurements for the rings and bore hole and the bore hole is original specs, should I do the piston rings? Could pouring that bit of oil into the head "fix" the compression issue permanently without needing to do all the piston stuff because it has been sitting un-running for a while now. Piston rings are expensive and new pistons and a re-bore is even MORE $$$... I already have MANY hours and about $200 into this bike. I really want to get this bike back to running and running well. Won't be a daily rider, but at least it wont be a paperweight.

 

FYI, my compression test was done on a cold engine, well it was 80 today, so not too cold. Any ideas on the stall out when i touch the throttle? Also, my choke cable is super tight after the rebuild.... like if i connect the choke cable, even when the choke is off, it opens the butterflies ALOT. Should i get it warm and retest the compression?

Shoild i check the valves even if the oil addition increased the psi to a suitable level?

 

Always do a valve check on unknown engine. Tight valves can give you a poor compression result. Did the choke cable pop out of holder at handlebar?
Compression test can be done warm or cold, throttle wide open, air filter and all plugs out and a good battery.

 

your carbs are another chapter. the "choke" doesn't open the butterflies. make sure the cables aren't reversed, it happens.
don't get into rings unless you have to, the rings may have been stuck from setting. it may fix itself.
i didn't see anything about a running sync, you need to do that.
while your doing things to make it go, you should be thinking about stopping things. like back brakes and front brake lines, dragging your feet don't work

 

The compression test was done to spec, except I left the air filter in.... is that going to make a huge difference?

Carbs are a whole damn book... those things gave me nightmares.. lol. The choke doesnt open the butterflies? there are only 2 cable connections... the throttle and choke... do I have them backwards? lol... darn, I will have to check. That could be why neither work properly... i hope its that simple, I will take the stupid error. This stuff is very interesting to learn alone, so I appreciate any input. Just wanted to get as far as I can with it b4 making a post. So many posts already helped me get this far!

I will be doing a running sync, my neighbor has a tool for it... so that is happening shortly. But I need to get it to idle and the throttle to not make it stall. I'm guessing its flooding, but unsure why, because I set the floats and fully rebuilt the carb. Only thing I can think is the screw on top of the carbs, behind the rubber plunger things, lol, that I dont know how to set properly, but it came new in the carb rebuild kit. OR of course the cables are backwards!

I will be doing brakes and such, but not until I make sure I can get it working without dropping $1000 into it. Then I will tackle the other things... ie Brakes, lights, customizing it...

I also have a 1978 XS1100 he left us too... that will be turned into a cafe if I can get this bike going. Cool stuff.

 

Mixture screw 1 3/4-2 turns out from soft bottom

 

The rubber plunger thing is for the enrichment circuit which does the work of a choke on a CV carb. When open it provides extra fuel to make the mixture richer. A choke reduces the air flow to make the mixture richer. Same result different way to get there.

 

Unsure what you mean by soft bottom... i screwed them all down, which was difficult... one of them never stoped screwing, i think it is stripped... and then back them out almost 3 turns. How important are these?

 

Very ! If they are damaged you’re in trouble .
Maybe get in contact with @hogfiddles
He is in Hubbardsville NY state not too far away. Worth the drive

 

Soft bottom is just enough to touch with 2 fingers on screwdriver.

 

****UPDATE****
I totally had the choke and throttle cables switched... whoops.

I replaced the oil, dark black yuck... put in 10w-40 yamalube. Also a new oil filter. Bike fired up, had choke half on. Idled for a bit, I then let the choke down and adjusted to idle screw because it was staying at about 2k rpm. got the idle to about 1.2k... tried hitting the throttle, it bogged again. Let it idle for a minute or two... tried throttle again, stalled. Tried to start the bike, it would not fire up. Checked spark plugs, wet and black. (these plugs were brand new last year) THEY ARE NGK-R if that matters, I saw someone say something about using Resistor plugs and cables... unsure how to see if they cables are resistor or not....

Checked compression... all were 100-110. Remember they were about that much b4 I put oil in the cylinder... which they then jumped 50 psi and the bike fired great after putting some oil in.

So... is it flooding? Do I have the wrong spark plugs? Could the piston rings be bad since now the psi dropped after I burned all the oil off? If it is flooding how do I resolve that?... Could flooding be caused by the piston ring wear? Unsure where to go with this next.... I was testing it on the center stand, if that makes a difference.

 

So it also looks like the spark is stronger on plugs 1 and 2... 3 and 4 spark, but not nearly as strong as 1 and 2... tested with the same spark plug across all 4 plugs. Could this be a problem work checking?

 

ok... so unsure what this means....

bike would not start .. I put the petcock to prime, waited 20 seconds. tried to start the bike and it fired up!. I let it idle on prime for a few minutes and it idled great, and responsive throttle... so then put the petcock on RUN, and it stayed ruining for like 5 mins, then I tried to hit the throttle and it bogged and almost stalled. so I put the petcock back on prime and waited 10 seconds, hit the throttle, no bog at all. so does this mean my petcock is not working properly?

 

Sure sounds like it is a petcock issue. They are rebuildable. On your spark plugs, I believe the correct number is bp7es. The plug wire caps unscrew from the wires, do this and trim about a quarter inch off the wires to ensure a good connection to the caps. While you have the caps off measure the resistance of them. They should be 5k ohms give or take a little bit. If they are out of spec replace them. This could contribute to the difference in spark you notice.

 

Cool, is there a procedure to follow for testing resistance? Or rebuilding the petcock? For testing, is it a bad thing to leave it on prime during vac sync or other things? Thanks for all the responses

 

Unscrew the plug cap from the wire, one lead into each end of the cap. I think there is a write up around here somewhere that covers rebuilding a petcock, perhaps someone more tech savvy than I can link it for you. In my opinion, as long as the bike is running during your tests and it obviously will be during a synch, I don't see an issue with it being on prime but definitely something I'd want to address.

 

so... took the petcock apart.. looked in great shape. I pulled air through the VAC, and fuel barely dripped out. I took the petcock apart further and tried to clean, fuel now drips a bit faster... set it to Run but after a very short ride it started bogging when I hit the throttle, so I put it back on prime, waited 5 seconds, and throttle became responsive again. unsure what else I can do to the petcock at this point.

my neighbor said it sound like a piston was skipping or not firing... I have no idea. it seems to lack power that's for sure, but I'm used to crotch rockets from the last couple years, so I don't know if it is running right or not.

also, there is a gold ball sitting next to the battery... he added a wire between the positive battery wire to the other side of that gold thing.. I guess it bypasses it. unsure what that is for.

some other things I need to address....

brakes, both front and rear barely work.
ignition and seat lock replacement
New front foot rests

 

First, great job Polock on guessing the cables were reversed!
Joshua, pictures, we love pictures. They're worth a lot of words.
When tuning the mixture on the carbs, I spent a lot of time checking plugs and tweaking the mixture screws. Not much when you get close, just 1/4 turn.. you'll get a feel for it. The bike should run strong and smooth once they're all running the same mixture.
There's a nice writeup on rebuilding the petcock in the "how-to" section. Might verify that looked like yours, down to the little details. Generally, if the vacuum shutoff doesn't work (in run position), it won't shutoff fully.