OldSoul67

I'm guessing the best way to get the pressure up would be testing out some oil restrictors to get it where I need. I had done some calculations for what the ring gap should have been for approx. 7psi however when i went and measured the rings they were already a little over that, but my piston to wall clearance was just about perfect. I don't remember off the top of my head what the measurements are but i've got them in a notepad for the bike.

I'll look up some numbers on that size and see what i can come up with, that might be a good option especially the fact that its ball bearing since the gs750 doesn't make a lot of oil pressure

I'll see if I can get in touch with those companies and see what they say. I already have my rings gapped pretty wide so i'm not too worried about that if i do go higher on the boost. Knowing me it'll be "a little more won't hurt" at some point, but ive got a gas station down the road that sells VP fuels and i don't take the bike out too often so I'm not against running race gas. I did see that dynatech made a digital points system but i wasn't sure if they had a spark control module to control timing as well or if it would be similar to setting up the points where its just the mechanical advance.

I'm looking at doing a turbo set up on my gs750. nothing to big just 5-7 psi. My two big questions is what size turbo would work best? and what's the best way to adjust timing? I'm still on the original points system. The top end has also been redone with a Weisco Big Bore kit making it an 850 with 10.25:1 compression roughly.

By the grace of who or whatever is above I had no bent valves, the exhaust valve seats were a little pitted and it looks like something small got close in the intakes of 1 and 3. Well I went for it and lapped all of the valves to see how much I could clean it up, the two intake valves looked better but still had some small indents the exhaust cleaned up great. So I put everything g back together and got 100psi on every cylinder. So it should work good, all I'm waiting on now is the new set of points to come in

I rechecked the timing and had to fight it skipping a tooth every time I tried to tighten down the idler pulley in between the cams. It is the correct 20 pins now lined up at the timing mark on the advanced side of the 1-4 mark. Looks like I'll be pulling the head off this weekend to see what I have in regards to bent valves. Hopefully I got away with it and just have to lap them back in. If not it looks like a new set and valve job might be in order

Thank you, I might need it. To me the bike was running good, but to be fair this is the first bike like this I've had so I don't really have a comparison

Yeah I wanted to make sure it would run well before running any power adders. The rings came out actually to what I was looking for to do about 10psi so I ran with it knowing it will lower the compression a bit, I was just planning for the future once it was running well so I didn't have to pull it back apart. But it looks like I am either way

Well after getting a little frustrated with it and letting the bike site for a couple weeks, I've found the problem, but I haven't been able to find the solution. I pulled the cam cover to see if anything changed as well as the head to replace the head gasket. First thing I noticed was when resetting the timing that I was 22 pins apart rather than the 20 I was supposed to have, easy enough fix. I checked my valve lash and was definitely too tight, so I re-shimmed the valves and now have .04-.05 clearence on the valves. The valves shims were the only thing I hadn't messed with during the original rebuild so I figured I had found it. Did a compression test again and had about 130psi on each cylinder, checked the book and said I needed a minimum of 100 so it looked good. Well half an hour of kicking later I decided to do another compression test and had 70psi on three of the four cylinders and 65 on cylinder three. I tried to add some oil to the cylinders to see if it would help and it did a bit, I got up to 80psi on each cylinder. I figured it would since the ring gaps are a little wide but I was planning to mount a small turbo later after I got the bike running well so it actually worked out where I needed it. Now I just don't know where I'm losing the compression at especially since my first test was good

I ended up pulling all of the ignition components out and cleaning everything so it all moves freely now, before it was a little sticky and I figured it was based off of the original throttle response and even after re setting the timing since the top end was apart

I usually turn it on for a few minutes before I take it out, it's definitely not a daily so I plan for rides and let everything fill up for a while before I actually leave. One thing I've noticed is once it is warmed up I have no problems starting it, but I've also rebuilt everything in the carbs including the choke plungers, I don't run ethanol fuel anyways but I used seals that are safe with it as well.

oh definitely if I don't shut off the fuel you can smell it for sure, however the petcock isn't vacuum anymore it's just gravity feed, most of the bike was in rough shape when I got it and that included the tank so it now has a tank with a vented cap and it's just gravity fed now, I made sure that it was above the carbs which isn't too hard to do with this frame design and increased the size of the petcock outlet and fuel line to help more with fueling. the original vacuum port is capped off.

the float bowls are carb specific from left to right, the left two are the same from what I can tell and the right two are the same, I can pull them off so see if there are are sort of drillings like what you're talking about but if i remember right I didn't see anything in the diagram for them

well, I got time to put some work in during the holidays. I pulled the carbs apart and re-cleaned them using chem dip and got all new needles and jets to replace some of the last original stuff that had definitely seen better days. Got everything put back together and bench synced and put back on the bike. once everything got adjusted to run I let it warm up and started adjusting jetting for partial, full throttle, and finally mid range. now having said that it is still hard to start and I have some ideas why. since I ended up going with a big bore kit for the 750 it also increased the compression to 10:1 along with raising displacement to 850. now when I originally put the bike together I was planning on it being a kick only bike, well with the starting issues i finally decided to put in a relay and rewire the starter. well, with the higher compression the starter is pulling more amps than it definitely should be and when the bike does try to fire up it pushes hard enough to even blow a 40 amp fuse, but it does try to start once it can get a few revolutions. Back to one of my ideas as to why its hard to start is because of the new compression, just kicking it over I don't think I can get enough dynamic compression and fuel at the same time to make it happy. I went through about 12 sets of plugs tuning it to make sure every major point of fueling that I can measure, from idle to going a little faster than I should down the highway was as good as I can possibly get it. yet I can still only get it to sputter without using starter fluid. I'm not really too pressed about the issue since I don't really daily the bike either, it just would have been nice to not have to carry around a can or two of fluid. I figure just with the higher volatility of the starter fluid that's why i need it just initially, maybe ill change out to some carbs later with some accelerator pumps to help get more fuel on start up. Thank you for all the suggestions, it's definitely not only helped me understand my problem but, learn a little more about how my bike is supposed to work which will only help me in the future.

I'll definitely go through them again when I get some time off, it'll probably be a couple weeks until I can get to it, but once I do I'll jump back on and tell every one how it worked out

They were stripped and dipped, then sprayed carb cleaner through all the passages I could find and had all new rebuild kits put in, new o rings, gaskets, jets.

The Points are working good from what I can see, I do need new coils, not because they're bad but the wires have definitely seen better days. I ended up re-jetting the pilot I was a little lean, after that I couldn't get it to start again. so back through adjusting the carbs, I did like you had said in an earlier response starting at one turn on the fuel screw and one and a half on the air. I couldn't get the bike to start until 4 1/2 turns out on the fuel, even then it wouldn't idle the air screws did nothing. i eventually got to about 6 turns out on the fuel and the air screws were picking up the idle and now it will finally run without the choke. so as of now to get it running the fuel is at 6 turns and the air is at 3. I'm not sure why I need such extreme adjustments to get it running

It's still running on points. The points are still original from when I bought the bike, both condensers however are new. The weights were a little sticky but still moved, I took off the weights and cleaned everything, I'm still having trouble. I finally got new pilot jets in so hopefully I can get them put in and get everything adjusted to see if it helps.

that's what I've been doing. I've been taking it to work for the past week since i finally got the title. I do need to get some seafoam or b-12 to help clean it out. Tried to fire it today without any starting fluid and it got close, but just couldn't get it. If it'll let me I might take it on a little trip this weekend and see how much it helps

I've cleaned the carbs a few times now, but I'll see if there's anything like that on these ones. These are the vm26 carbs and from what I found before the early 850's used the same carbs just with different jetting. I've cut a couple sets of plugs now, the latest ones are a little rich on idle, but I've got the idle circuit adjusted pretty far out right now. It's trying to start now but still not quite enough to get it going yet

It didn't run great, however I didn't get to ride it either, the wiring was cut up so I had to rewire the bike to get it started. I just followed the factory wiring diagram to redo it. After I got it started is when the carbs were rebuilt and I didn't see much of an improvement so that's when I checked compression and the top end rebuild was done

I have, I figured it was an initial fueling issue and after sitting for a couple days I leave the petcock open for a few minutes to make sure the bowls on all the carbs would be filled.

They were at 3 turns out and 2 turns on the air screws , but I've adjusted them 1/4 turn at a time from just a half turn all the way to where the screws are about to fall out. Each time I'd get to 2 1/2 turns on the air screw I'd go another 1/4 out on the fuel and try again starting at 1 1/2 turns on the air screw each time. The tips of the screws aren't broken off, I checked that when I replaced the original ones. The pods aren't blocking the air passage at the mouth of the carb, I still had the same problem running no filters at all whenever I got it running after the rebuild

it definitely revs once its started. I got a chance to tape up the pods, however I didn't get any time to try and adjust the fuel/air so if I can get more time tomorrow or soon after can confirm if it helped or not and go from there

Taped up the pods this morning, but I didn't have time to mess with the air/fuel so I don't know if it helped yet. will try again tomorrow if I can get some more time to mess with it