19:37 on 1 of my carbs, that small rubber plug out of the 2 you pulled out is damaged to the point where only the piece that goes in remains. what are those called? i want to replace it assuming it wont provide a proper seal seeing how damaged it is. Great videos! loving this series.
Jonathan-David Pieter Heij Thanks, glad it's useful. I don't know if that part has an official name but it's essentially a rubber bung. You can't just put anything in there though as it has to be resistant to petrol. It's possible they might be included in a carb rebuild kit for this model carb, if not a carb specialist should be able to locate a suitable replacement. Sorry I can't be more specific there.
after some digging i found the part numbers for the main jet and idle jet plug. they dont come cheap but i went ahead and ordered replacements for both carbs. I these dont come with a rebuild kit. ill list the official makuni parts numbers below so others can find them. Main jet plug: N167031a Idle jet plug: N167032 Cheers!
Got another question for my 95 Yamaha Virago 535SG. For the main jet sizes the manuals say 137.5 front cylinder 135 rear cylinder. But online Yamaha diagrams it shows the 135 in the front carb and 137.5 in rear carb where throttle lever is. So why do the manuals say front cylinder 137.5, rear cylinder 135? Isn't the front cylinder behind the front tire and the rear by the back seat? I have someone telling me the rear is the front and the front is the rear, I know (from rear to front of bike) cylinder numbering is 1-2 which I thought was firing order idk. But I also see that in the book it says to take the "front carb" enrichment diaphragm off and that's before you split carb. So I'd think that the front carb goes to front cylinder and rear carb (where gas goes in first) is going to rear cylinder, right?? I'm just so confused 🤔
You would logically think front to rear so yes front cylinder to me would be behind the front tyre but it might be named based on the firing order, now it's a while since I've owned or worked on one but it could be that the firing order is 1-2 (rear-front) but the manual really should specify. However, logically the larger jet should be in the rear because it will naturally run hotter and therefore leaner than the front which is exposed to more cooling air in motion. Sorry I can't get l give you a definitive answer on the numbering but larger jet to the rear certainly.
At the 7:08 point in the video, you can see a small, black, right angle fitting at the bottom left side of the carburetors. It is the farthest left item on the carb from that angle. Is that a drain port for the fuel bowl? Is there supposed to be a hose connected to it for vacuum or something? My bike is surging and popping. I thought that that black fitting might have been one of the vacuum ports that was not plugged and causing my problems. But, the vacuum ports are on the rubber carb holder that mates the carburetor to the intake manifold. On my bike, one port is plugged and one port has a rubber hose going to the air injector for emissions control. Now, I was wondering what that small, black fitting is. I got a feeling that diagnosing what is causing my bike to surge and pop is going to take a lot more sleuthing than I initially thought.
You seem to be the best source on Mikuni carbs.. Any advise removing float valve seats from those carburetors? I always liked Seiko Automatics. Great channel subbed and like all vids i watch.
Thanks for the kind words, I don't know about being the best source on them though. I'm used to Mikuni as they're so commonly used on many Japanese bikes. Sadly I've no help to offer on removal of float valve seats. Perhaps heating the carb body in the oven to allow thermal expansion to do the work for you?
@@spidiq8 Tried heat. Might work on some. 1994 xv535 same carbs. Got one out. Need a 4mm tap and 3.3mm drill. There's a cap cover has to come off first. No replacement part in rebuild kit. The cap is around 6mm thick before getting to strainer screen on top of seat. I drilled all the way thru cap, threaded hole and fashioned a puller with a 3/8 drive socket, bolt, and washer/spacer depending on bolt length. Repeated for seat. The new seat in All Balls rebuild kit does not fit real snug. The problem is getting in there to clean an old one. Access is limited. Don't know what i will do for sure to finish, but i think it easier to fashion a flexible shaft steel wool holder to clean the other seat. Even that will not take out a scratch tho'. Quite a dilemma none the less... Thanks for responding.
@@BugsWisely That sounds like a pain. Glad you got somewhere with it at least. The carb design on these is the only real bugbear I have. I think a single carb and y inlet HD style would be a great idea.
Hello, Don't know if you still have that motorbike but could you show me (or point me towards a video already existing) about how to put the carburettor back on the motorcycle? Thanks. I have a bobber (a cheap motorbike I bought to train on mechanic) I cleaned the carb but I CAN'T find a way to put it back and I think it is probably set similarly on your bike (I hope). Thx.
This one wasn't mine. I was working on it for someone. There is a refitting video however. If you check my playlists you'll find a motorbike mechanical list which has all the bike related videos in.
Hey, could you possibly tell me what could cause the following happening: Rarely but happened 2 times lets say for 100 ignitions total, while starting for the first time that day the throttle revs up on its own to the max. Choke was slightly engaged, after which i power off and try again without choke and happens again. Few minutes later fixes on its own. Another thing i noticed while running warmed up and everything, if i hold the throttle just at just about the point where the cable pulls over the idle it actually revs up slowly as if i were increasing pull. Throttle goes down rather slow after releasing the throttle. Diagnosis i had so far, the carb adjustment screw had been broken off and "glued" in place so one of the carbs might be off sync. Also is there a fix for this screw any tips? thanks in advance
Your carbs certainly need looking into. For the broken screw, that's a problem, it will need to be removed, thread and seat checked and replaced. That might require drilling and an extractor. The way a CV carb works is that they cable opens the throttle butterfly, this allows airflow, the increase in airflow through the venturi causes the slides to rise, these slides are damped with rubber dampers and spring pressure and they raise a needle which allows more fuel through to mix with the air. Something is either sticking, partially blocked or similar, or the rubber diaphragms are holed which is common and if the mixture is off and thereby the balance this will cause a fluttering effect between each carb as the piston moving wants to draw in air but if they're imbalanced the fuel air intake will be uneven.
At 3:58 to the bottom right of each of the two big holes there are these brass looking round things. What are those? After a carburetor clean, mine started to leak fuel from these spots, every time I start the bike up and it continues while it's running. I'm not quite sure, but are those spots directly above the needle valve? And if so, could the needle valve be responsible for the leakage?
They're press fitted caps similar to core plugs and shouldn't be leaking. Are you certain the fuel is coming from there and not elsewhere and dripping from there after running to them?
@@spidiq8 Yes. My friend and I could see it perfectly on both sides, every time we would start up the petrol pump. The weird thing is, we've adjusted one of the floaters and the problem has all but disappeared. We think it disappeared on its own and the floater had nothing to do with it. I'm checking it after every ride right now. Hasn't leaked again, yet.
My ex wife named her and yes it's because of Gremlins when she was a kitten she was a spiky black floofball with big eyes and as I was thinking of a name my ex said 'she looks like a gizmo' so that became her name.
Low end is mainly your pilot jet, mid to high is controlled by the vacuum and diaphragms and needle valve. Check your diaphragms for splits and holing, which is a common problem. Check needle height settings and jet sizes. A plug chop will give an idea of running. If you're unfamiliar Google plug chop how to for a detailed explanation.
Hi mate, do you know what is the size of the jets you removed (12:50)? My bike is having problems and I believe it is due to the size of the jets. Thanks a lot
@@leonardovanella2735 As far as I remember yes, the only time I've seen different jet sizes are mains on some inline fours where the centre pair are slightly larger.
Because they're sideways if there's any seepage of fuel or the floats or before valves stuck etc it can creep in. I've seen many with tide marks and pinholes in the diaphragm lowers as they sit on the bike.
@@spidiq8 could it come from the o-ring under the jet block for the emulsion tube or the washer on top holding it down? The slides and lower boots were saturated.. they shouldn't be right?
@@spidiq8 oh you're talking about the needle valve? Can messing with the floats for fuel level measurements cause this too. Bc they're all brand new and don't stick I did set it to high a few times on the front carb and no fuel came out and I've been having a issue with getting the fuel level right ughh. I ordered new o-rings for the emulsion tube that goes under the jet block and I guess seals where that tube goes in to carb.. I've seen 2 people put the o-ring on the emulsion tube then insert it through the bore of the slides. But my 3 books says that it goes the other way and I've seen videos of disassembling the jet block and tube and the o-ring is always underneath the jet block on the emulsion tube but not on the bore size. And I used the o-ring from cheap Chinese kit and the o-ring was skinnier then the original that had been in there before. So I ordered real Yamaha o-rings and gaskets again...
@@firebird14420 When it comes to fuel it's always best to use OEM seals. Setting the float height wrong can cause excess fuel but it should come out of the overflow first, it's always possible the overflow tube or vent is blocked and from here fuel can get into other areas of the carb but the worst possibility is if it gets into the bores as it'll SEO seep past the piston rings and into the sump. This is usually quite obvious as your oil level will rise and removing the filter and sniffing will tell you straightaway if there's fuel in there.
I took bike to mechanic to fix bc of syncing the carbs, fuel level adjustment, and I have no compressed air. He's had it in a ultrasonic cleaner for 3 weeks and said only one slide has moved and the other hasn't causing the throttle not to move...
No, in a CV carb (Constant Velocity) the throttle cable isn't directly linked and they're worked by vacuum. the bike won't run properly if they're stuck though. if the the seizure can be the throttle grip, the cable itself or the linkage on the carb body. Has it been sitting outdoors for a long time?
Thank you for the helpful critique. My cat however had fairly coarse but incredibly soft smooth fur however and she inspected each carb thoroughly for serviceability before the refit. ☺