Do I need to replace my base gasket?

[chuck hahn]

Roll it around again clockwise from the points side and watch the number 1 intake cam. Lobe will open the valve and when it comes up and close the valve you are on the compression stroke. Ever so slowly bring the piston to TDC with a screw driver riding up with the pistons rise...youll feel it start to slow down. Now is the critical time to be very gentle and watch for the T mark to line up with the case mark..AND also be feeling with the screw driver at the same time. When the T gets just about inline with the case mark, you should feel that the screw driver has also come to a dead stop. Being just a tick past TDC is ok...but just a small tick at that !!! I will PM you my number and you can call in real time with me on speaker if you have troubles.

[Ian Donahue]

Update: So I got a good idle in the garage, so I put seafoam into the cylinders and let it rest a couple of days, then i put everything back together and took it out tonight, hoping to start an Italian tune up and shake the rings free, and improving my compression problem. But even though I had good idle, I could only go a couple hundred yards before the bike stalled. I was also having a hard time with power. So I used the choke to keep the idle up to get it home, but now I'm unsure what to do next so I would like to ask the more experienced among you what I should do next. Sounds like a top end rebuild right? I don't mind, but I don't want to do it if that's not the problem, of course. So a quick poll - if you were me, would you rebuild the top end, or try something else?

[bobgroger]

Update: So I got a good idle in the garage, so I put seafoam into the cylinders and let it rest a couple of days, then i put everything back together and took it out tonight, hoping to start an Italian tune up and shake the rings free, and improving my compression problem. But even though I had good idle, I could only go a couple hundred yards before the bike stalled. I was also having a hard time with power. So I used the choke to keep the idle up to get it home, but now I'm unsure what to do next so I would like to ask the more experienced among you what I should do next. Sounds like a top end rebuild right? I don't mind, but I don't want to do it if that's not the problem, of course. So a quick poll - if you were me, would you rebuild the top end, or try something else?

These sometimes have low compression after a long nap. My 15k mile 850 was in the 60-90 range when it woke up, after 2000 miles it is 150-170. I think you still have some carb problems. See if you can adjust the idle when it is hot enough to keep it running with a reasonable idle with the mixture screws 2.5-3 turns out, airbox and tubes sealed, air filter in place. Ride it as much as you can, even if it doesn't run great. See if the compression comes up. If it was just one hole I would give you different advice. Another often overlooked problem is a stuck timing advancer. You should be able to turn this by hand. WD40 or NutzOff should fix it

[hillsy]

Your model doesn't have a mechanical ignition advancer, so that wont be the problem.

Have you cleaned / checked your carbs at any stage? I would be thinking if you can get it to run with choke then it's more than likely a fuel related issue.

[Ian Donahue]

Yes, I have cleaned the carb, as per the bikecliff tutorial, with o-rings from cycleorings.com. Also airbox rebuild. Valves were shimmed. Plugs changed. I am going to swap out the petcock tonight, I'm hoping that will help. As I read some of the other posts, I'm learning the language for discussing this - Although I have idle, it's dying when I give it gas. It will run for a minute, but then die. I have aftermarket needles and seats, my OEM sets will be here next week. Could that be it?

[Ian Donahue]

These sometimes have low compression after a long nap. My 15k mile 850 was in the 60-90 range when it woke up, after 2000 miles it is 150-170.

That's good to know - so the bike should run (but not well) even at 60psi? That means I'm still chasing fuel delivery issues... Thanks Bobgroger.

[Ian Donahue]

Update #something: In case anyone is still following along, things are going well with my 850! My stalling problem was the petcock- when I switched to prime it ran better, and I put 100 miles on it over the weekend, very exciting. Couple of easier questions:

Choke - my choke seems to be "binary". It is on, and the revs (when cold) jump to 3500 - 4500, and when I gently slide the thing over, it stays the same until the choke is off and the idle comes down. Is this the way the choke is designed, or do I still have carb issues? Also, what do you think of warming up the bike at revs that high? Seems a little violent.

Idle - after warming up and riding around a bit, I will have issues with a rising idle, if that's the right word. When I clutch in at a stop sign or a light, the idle climbs up to around 2500. A quick blip of the throttle brings it back down to 1200, usually. What is this a sign of? Vacuum leak? Carb issue? I have replaced intake boots and o-rings, and rebuilt the airbox (stock). Any thoughts?

Anyhoo - thanks for all the help so far, wouldn't have even known where to start without GSR!

[eil]

Choke - my choke seems to be "binary". It is on, and the revs (when cold) jump to 3500 - 4500, and when I gently slide the thing over, it stays the same until the choke is off and the idle comes down. Is this the way the choke is designed, or do I still have carb issues? Also, what do you think of warming up the bike at revs that high? Seems a little violent.

That's pretty normal of the GS chokes from what I've seen. Very touchy if you want somewhere between no choke and full choke. When I start my 850, I start it on full choke and then stand there for a good 30 seconds slowly pushing it in until it settles around 2000 rpm. By the time I put my helmet and gloves on, it's usually up to something like 2500. I ride away on that and push the choke in once I'm out on the road.

I don't think there's anything wrong with warming up at 4k rpm. It's just a bit noisy is all. Can't see how it would hurt the engine. Although it's probably easier on the transmission to have the RPMs down more in the 2k range for the initial shift into first gear.

Idle - after warming up and riding around a bit, I will have issues with a rising idle, if that's the right word. When I clutch in at a stop sign or a light, the idle climbs up to around 2500. A quick blip of the throttle brings it back down to 1200, usually. What is this a sign of? Vacuum leak? Carb issue? I have replaced intake boots and o-rings, and rebuilt the airbox (stock). Any thoughts?

Classic sign of a vacuum leak. Sounds like you've done the obvious. Did you replace both sets of boots? Are the carbs synced? What kind of air filter are you running? Did you tighten the screws on the sync ports of the boots? Is the petcock vacuum line on carb #2 connected or blocked off?

[Ian Donahue]

Thanks Eil. Yes on all maintenance, including a Morgan Carbtune. The air filter is the one that came with the bike this winter. I cleaned and oiled it during the airbox rebuild and resealing. I have low compression, about 70psi, although it is improving with mileage. When I spray starter fluid near the base gasket, the revs go up. One theory is that are is getting sucked in through the base gasket and then past the rings, which obviously aren't seated correctly yet. Sound crazy?

The vacuum line is hooked up to my petcock. Doesn't it have to be? Should I try plugging it and running on prime? I replaced the hose to make sure it didn't have a 30 year old pin hole in it.

Been chasing this vacuum leak for 2 months now... Any advice would be appreciated!

[JTGS850GL]

My 850 fires up cold on full choke and goes right 4000 rpm. I can turn the choke down to 2000 rpm immediately after it starts up. Within 30 seconds to a minute, I can turn off the choke and ride off. How well your bike warms up and rides off is very dependent on how well your carbs are set up and your valves are adjusted.