gorbys

It's stamped right there on the cam wheel. 451.

Short video of it idling and a little rev. Probably still a bit fat https://youtube.com/shorts/rJWhrDFmxP0?si=OPjBRL2MNHBxBtLJ

I couldn't get all this to add up with the low compression. Like why would it be so bad if the piston rings where new,valves lapped.... so I checked timing and... bingo! Cams where off. I don't know, maybe the crank moved when they where installed I redid them and boy did it make all the difference! After some fettling with the carbs and idle i had it sitting at 1200 for minutes! Damn steady! I'm delighted! Will sync the carbs tomorrow, recheck ignition timing and compression. Take a test ride

Just the standard set of four gauges with vacuum hose. Neat tip. Will try that.

I do have another set of cv carbs on the shelf from the older gs850, but they are in no shape to be run as they sit now. They need a complete overhaul. Maybe I should just order some parts and get to work on them. They weren't ultrasonic cleaned as my cleaner is dead (just ordered parts to repair it though). But all the jets are new, and I made sure to blow brake cleaner through all the circuits to check that they where open. Which they all where. I also posted about this in a classic motorcycle group on facebook over here and one guy replied that he had a 82 1100 gsx that would behave exactly the same! And his problems disappeared after refitting the original airfilter box. I don't have the standard box, is there some other way to simulate this? Socks over the air filters? Sponges inside? Taping off a portion of the inlet??

Gonna do another compression test today and try to add some oil to the cylinders see what happens

Was checked when the carbs where disassembled and later when I adjusted the needle height. Pops, true, but the exhaust is a straight through exhaust so pops and bangs aren't uncommon since there is no dampening around 100-110 psi EDIT: okay, so I see in the service manual now on gsarchive that standard is 128-171psi. Limit is 100psi. Out of the many indicators of malconditions the only one that sticks out to me is "poor sealing of valves" as the piston rings where replaced and cylinders honed when I bought the engine but not the valves, they where just lapped. But they didn't look good and should have been replaced but time and money wasn't available at the time. Have we reached the consensus that low compression is to blame for this? Valves and poor sealing does pop up under "Engine idles poorly" and "Engine is hard to start" Perhaps cams are misaligned? I Think I should have another look at that too

I did that today as well. Looked alright. Checked valves probably a couple of times last year they're all within spec. Checked float level when they where apart last time so that's in spec. Also replaced all o rings on carbs.

They where fine before winter and it had the same idling issues then so

Yes. And yes.

So I did that, I turned them all in, started it and set the idle adjustment screw so that it would idle without me holding the throttle. So now we're at 1500 or so rpm's. I turn them out 1/4 turn and wait for the rpm's to rise and they do and I continue to do so until its screaming at the neighbours at 3.3k rpms at which I then adjust the idle rpm down again. Perhaps this was wrong? should I just have continued upping the mixture until it doesn't go any higher? I have neighbours all around and 3k + rpms is frigging loud on a 4-1 with no db killer so I'm genuienly concerned about complaints at this point. Regardless, back to somewhat reasonable rpms and I try to adjust some more but it doesn't get much response. And now begins the weirdness: I adjust the idle to a damn steady 1000rpms and it holds it for i dont know a minute or two and I'm all giggity then all of a sudden there's a little pop and it starts to race off up up until its now at 2200 at which point I back out the adjuster to bring it down again, then it almost dies and I turn it in and get it sitting at 1000 again but that only lasts for a short time before it dies. And several times I got it sitting at a lower idle, 1000 one time, 1200 another time, but all of the times it only last a short while before it either races off the moon or just dies. I did all this with the tank removed and i watched the adjuster sometimes as i turned it and i turn it a little bit; nothing. A little bit more; still nothing, just a hair more: too much! Would be pulling my hair out if only I had some left! No that's not sticking, returns as it should and there's freeplay

If the idle is at 1500, and I rev it, it will rev and then settle at 1500. If I try to lower the idle to say 1000 and I give it a rev as it's about to die it will rev, hang at about 1500-2000 and then drop down and die again. You suggesting I give it some more fuel and then see if I can manage to drop the idle a bit to?

I have a 77 GS750 with a bandit swingarm. If you go wider than stock rear wheel the problem is you can't easily just offsett the front sprocket as the entire clutch release mechanism sits in the way. So it's either swapping to a gsx engine or a gs1000 as mentioned, or there are spacer kits as mentioned in another post here. Chain and frame clearance also becomes a slight issue with a 180 rear wheel

Last year was the first season properly running the gsx1100 engine in my gs750 and I spent so much time troubleshooting heaps of stuff without ever finding the root cause as to why I can't get a stable low idle on it. Yesterday I had it running again and I was reminded of this very annoying problem. It seems like every time I ride I have to adjust the idle rpm, sometimes even during a ride as it will be fine when I take off and then when I pull over it's too low, or to high. Yesterday I got it running, warmed it up, bike idles high as it should on choke. After it's warmed up, choke off, it's idling at around 15-1600 rpm, and I want it to sit at 1000-1100. So i adjust it down with the idle screw until I get to around 1000, where it will sit for a few seconds before dropping to 6-800rpm struggle and eventually die. Now if I instead of letting it die I try to save it by giving it some throttle and revving it it will rev up and then it will usually settle at 1500 again for a short while before dropping down and eventually dying. When adjusting it it seems like there's not enough "range" on the adjuster to get it to sit where I want. Like it's either 1500+ or 7-800 and subsequent death. Nothing in between no matter how minute of an adjustment I make on the screw. It's just so infuriating, I had a gsx750 for a couple of weeks last year and there was nothing like this, I adjusted the idle and thats where it sat. Granted that was a mostly stock bike. The 1100 has a full exhaust and K&N filters. But still, the 850 8v engine that was in it before also had exhaust/pods combo but idled like stock. Any ideas or tips to try out? -cable linkage is working smoothly -carbs have been cleaned and synced -rubber boots and clamps are new -can't find any air leaks when spraying around carbs and boots Also to note: sometimes if I its idling at 1500 if I put it in gear and relase the clutch in to the friction zone and back in the idle will drop down to less than 1000.....

Yes i fixed it by replacing the 750 engine with a gsx1100 engine

No I didn't, thanks for the info. I was gonna but I didn't have the correct size adapter for the spark plug hole. No. You're right, they might be bad. I remember I experienced spark blow out on my Datsun due to bad plugs now that you mentioned it. Anyways, I don't think I'll be fiddling anymore with it now. I don't have the time and space for it at the moment so I've put it up for sale. If it goes it goes, if it doesn't then maybe I'll come back to it next year when it's hot again and we get our three days of summer.

I've found one carb leaks, and the petcock leaks in the on position. So I'll bet the fuel level in that one is to the max! Also noticed a bit of smoke today when I started it up. So we have at least to high fuel level on one and possible some oil burning. Weird thing is I watched a video yesterday I took from last week where I did a pull from standstill and it was freaking flawless. It's like it worked alright right after fixing the carbs and then it's gotten worse the more I drove it... Yes. The where clogged as well. Had to poke out every single hole on every single tube... I'm starting to think it needs another clean out. Like something has loosened and clogged up something.

Drove pretty much the same route again with the new plug caps. Not sure I felt that much of an improvement. I mean the plugs are indicating a richer condition but it still doesn't feel like it pulls as hard as it should. And number two carb is leaking fuel through the fuel needle so maybe that's why it's not going as good, since it looks like it's drowning. Edit: I did a couple of pulls 1-2 gear to redline and when I hit 8 or 9.5k rpm it kind of stopped, then came back again. Like a really lazy rev limiter. That's not right either I guess.

So. I checked the ignition system. And found out that all the plug caps are wack except for one. Primary resistance is good in both coils. Secondary was way higher than specified. One was at 70k ohm and the other one at over 800k ohm(this is the one that supplies plug 1-4) The one plug cap that was good, was number two. Coincidentally the same plug that shows a little bit richer mixture than the three other. So weak spark=lean burn? Secondary resistance with caps removed checked out at 11k ohms on both coils so they're good. I'm gonna try with the caps off of my 1100 since they're pretty new and see if it goes any better but is there any thing detrimental to using 5kOhm caps instead of the oem 11kOhm? I haven't noticed anything on the 1100...

I know this. The numbers I mentioned are mikuni numbers. And yes dj kits have adjustable needles with different tapers. But none of that matters since I can't use the dj jets anyway. Cheaper as well to just buy four new mikuni jets instead of one more dj kit Yes, every thing that could be taken apart was taken apart and cleaned, poked and blasted. Dyno would be great but this is Norway. I know of one, and that's a cross country trip for me...

One would assume so, I haven't heard anything about this when browsing the Web. Anyways, browsing the dynojet pages I have found a kit for the 750 and I have checked the installation manual but unfortunately the jets recommended doesn't match the extra jets I have. So I have to buy new ones. According to this guide I need to go up two sizes. https://www.caferacerwebshop.com/en/blogs/blog/how-to-rejet-your-cafe-racer-carburetor/ If my stock ones are 112.5 that would mean a 115 jet right? But should I buy a set of 117.5 just incase? I need to order from the UK so shipping takes a while.

Sure you didn't get the wrong jets? No issues seating them in the 1100 carbs and I just compared the spare ones I have to a genuine mikuni jet and threads are the same. Screwed them both into the bs32 carbs I have on the shelf no problems.

What do you mean? I have dj mains in my 1100 with the stock tubes.

Weak? As in a weak spark? Carbs are stock as far as I know, I'm gonna double check the main jet as I forgot to check size when I had it apart. But I'm pretty sure they're stock. No i don't have new sparkplugs laying around so no not a proper plug chop. Just 30-40mins of high speed driving and wide open throttle pulls. But in general I feel like it needs more fuel under wot. I realise in hindsight I should have tried some pulls while giving it some choke to see if it helped but one can't think of everything when you're freezing your balls off on a late night

Hello folks! I rescued a 1980 GSX750 last month from a garage where it had been sitting for the last 5-6 years... I cleaned the carbs and got it running, and now the fun begins... Basically it starts and runs fine. But acceleration is sluggish. I rode it in anger on the backroads here for about 30-40 minutes and checked the plugs, 1-4 where white, 2-3 had a little bit more color but not much really. It pulls great from the get go but then as you roll on through a quarter to half throttle and beyond there's a noticeable change in behaviour as you get on the needle and main jet. Twist the throttle from off idle and acceleration dips at 4k rpm. Every time. And from there on it accelerates but it feels lacking. Especially in higher gears. So white plugs, blue pipes, lean condition right? I believe someone has swapped to a 4-1 exhaust but never rejetted. Because it should be rejetted right even if you still have the stock airbox and filter? OR? Is shimming the needle an alternative? Or in case of rejetting; I have a dynojet kit that I used on my 1100. I used the needles and the stage 3 jets, which means I still have three jet sizes left over in that box. Can I use those dynojets with the stock needles or is that a no go, I need proper mikuni main jets as long as I use the mikuni needle?