First highway run; engine bogs at 60

[Brassneck]

For what it's worth...taking the carbs out and off the bike may be the hardest part of the cleaning. Ha ha...I'm joking, kind of. The removal of them is/can be a tight fit and you have to get everything out of the way to do it. But it's not impossible, nor is it all that technical. For the cleaning: If you have some cleaner (personally, I like brake cleaner for cleaning carb parts, it doesn't seem to hurt rubber and leaves no residue...I only use carb cleaner for the jets themselves as it helps dissolve crud a little better and stay away from the rubber with carb cleaner- per the warnings above), and then some wire (like from a steel brush or something thin like that), with a little air (can of air will work...not the most powerful, but will suffice) you can clean out the carbs, jets, etc. in a few hours no problem. You may even be able to use everything that's in there. Granted, it would be good to have back up o-rings, etc. in case you need them...but if it all looks good after you've cleaned everything you can reuse. Chances are your jets and all internals are fine...just dirty. My point is that it is something that you can do on like a saturday and be running by end of day. And if you get good at it, like many do after doing it a few times (ha ha)...you can do it all in a morning and out running around all day chasing something else that happens to need attention. Ahem...which never happens on these bikes, of course.

 

[Brassneck]

There is a lot of info in the forum on cleaning carbs and how to's. There are also a few vids on youtube (which helps visually get a sense of it) that you may want to check out. Not sure which carbs you have, but the concept is the same. This will help give you some perspective on what's inside the carbs and parts to be aware of. Note, not the greatest how to video...but a good place to start:

Then, after you've cleaned them...you'll likely need to sync them, and reset air/fuel mix screws, etc. Before you take any adjustment type screws out...check how many turns each screw takes to bottom out. write it down so you can put them back to the same spot. I'm sure there's other things to consider too, but I'm drawing a blank for some reason. (getting old sucks).

Anyways, good luck.

 

[tzimmerm]

Ok. Well, I don’t have an air compressor, but I do happen to have a couple cans of brakleen, and since I’m replacing the manifolds, Taking them out shouldn’t be too Horrible, because I can just take the manifolds out at the same time. I remember getting the carbs on/off my chopper was a pain in the ass, and I didnt even have the air box or anything else to contend with on that. Well, looks like I know what I’ll be doing this weekend instead of riding.

 

[tzimmerm]

Allright, getting ready to leave work. Wish me luck. Hopefully I make it home.

 

[robinc]

Of course my bike is an 81 with BS34s which are linked together on a common shaft so one piece of cardboard opens both carbs by a small fraction. I cannot remember if this technique is as easily implemented on the other carburetor setups.

Paul ever since reading of this tip of yours I have been using it on the 78-79 BS38'S on my 77D and 78E. Works a treat.

 

[tzimmerm]

Well, the damn thing won’t even start now. It started with the choke several time. It revved up high all on it’s own while idling but then it died. Now I can’t get it to fire at all.

 

[tzimmerm]

Okay! Update! An age old lesson that apparently we all forgot- always check the simple stuff first. When the bike wouldnt start, as a last resort I pulled the fuel line from the left petcock to see if it was plugged. No gas was coming out! I have been in the habit of riding with the petcocks on “reserve” instead of “on”. I switched the petcock to “on” and fuel came pouring out! I immediately switched the right side to “on” as well, and hit the start button. It fired right the fuck up with the choke off! It ran awesome all the way home, just like it should. I should check the right side as well, but My theory is now that the left petcock became clogged at some point yesterday, probably on the interstate. The right side however was flowing fine, so I was probably running on mostly one carb. Today at lunch the left must have been totally clogged, but when I gave it throttle the right had enough fuel to make it run, but the left would be sucking in so much air it would over rev. I will go for another quick ride here in the next hour up to the next exit to see if it can reach 65, and if that was my problem all I need to do is rebuild the petcocks! PS- here are pics of my carbs right before I discovered the clogged reserve petcock.

 

[Brassneck]

Okay! Update! An age old lesson that apparently we all forgot- .

Uh...well, not all of us. Ha ha.

It could even be a clog in your petcocks...might even start there.

In all seriousness, glad it was a simple issue.

 

[tzimmerm]

Ok, good call. Someone did mention it. Sorry!

 

[5twins]

Your carbs look quite good (clean), on the outside anyway, lol. Your petcocks have 2 pipes sticking up out of the tops into the tank. The Reserve feed pipe is very short, the Main feed pipe is taller. You may need to clean more than the petcocks, you might need to flush the tank out too. There could be a large build-up of crap laying in the bottom of the tank and that is what may have plugged up the Reserve pipe.

 

[Paul Sutton]

As said by 5twins, WD40 blown through the straw works really well on cleaning the fine passages in the carburetor. That was what I used on mine. Basically the WD40 is my compressed air supply and the oil part is mild on rubber. White spirits is harsh on rubber components. It will swell the diaphragms to about twice their normal size. I made this mistake once cleaning the dust seal around the slave cylinder on the front disk caliper. I try to clean with what even the rubber gets exposed to, so for the carburetor I use mainly petrol.

Why do you use the octane additive? I think this is an interesting topic.

 

[peanut]

good to hear that you made it home anyways.

As 5Twins says the carbs look really clean which would suggest that they have been off, stripped and cleaned fairly recently. Even though, it is easy for tiny jets, filters and orifices to get clogged very quickly through the bike standing unused for a while and not having your fuel filtered adequately.

I notice that you do not appear to have any inline filters fitted ... this is an absolute must do whatever else you do on the bike . There is always a sediment of very fine rust inside old gas tanks which will gradually fill the bottom of your fuel bowls and block your idle jet and needle jet atomiser holes. You do not want to be taking your carbs off every few days to clean the fuel bowls and idle jets etc

These are the filters I use. They are a little on the large side but they have a large filter surface area which doesn't restrict the gas flow ,they are a quality inline filter which lets absolutely nothing through except your gas.
https://www.ebay.co.uk/itm/x5-Petro...mm-8mm-pipe-/321134080145?hash=item4ac5153091

 

[tzimmerm]

I will add some fuel filters. Good call. And Paul sutton, it’s probably overkill, but I was reading in the forum about how these engines were designed to run on 94-95 octane, and the higher the octane, generally speaking, the better the engine will run (assuming timing and everything else is right). So I filled a 5 Gallon gas tank with premium (or supreme, lol) and added octane boost to make sure my baby was gettin the sweetest juice I could give her.

 

[xjwmx]

I use 87 and have tens of thousands of miles w/o a problem. I have retarded the timing a bit (yes, possible on a Special), w/o that it would ping under stress even with 93. No noticeable difference in power. Have read alcohol raises effective octane so am suspicious of high octane to begin with.

 

[aldo5468]

Yes, ethanol does contribute octane value to any ethanol-gasoline mix. Refineries for many years now have been making an 84-octane "BOB" ("blend-for-oxygenate blending") for US consumption that when mixed with 10% ethanol just prior to delivery to dispensing outlets gives 87-octane regular-grade "E10". (These are US "pump" octane values; i.e., the average of RON and MON octane levels for any given sample.) BOB for premium E10 is produced with somewhat higher octane so that the mix is legally salable as premium. E15 would have an octane level about the same as E10 mid-grade.

 

[tzimmerm]

Ok, so I added inline fuel filters to the lines. There wasn't much room, and I ended up with a kink in the left side fuel line, basically replicating the clogged petcock. I didnt realize this until after I took another test run down the interstate, just up to the next exit, about 1/4 mile. It made it up to 70 this time, but bogged down after a second or two. It picked back up at 55-60, like last time. So I redid the fuel line on the left with clear fuel hose this time, and successfully routed the kink out. I think the petcocks are probably gummed up or clogged, so my question is this- am I better off replacing both petcocks or buying the rebuild kits from mikes? The rebuild kits are half the cost, but I read a little of the petcock rebuild thread and it sounds like a hassle. Mind you I have a ‘77 without vacuum, but the polishing and all that just doesnt sound like fun to me. If new can be depended on, it would be worth it to me to pay twice as much for the convenience of just bolting new ones on and going.

 

[peanut]

I always use clear fuel lines now . They allow you to see exactly what is going on with fuel delivery at a glance , air locks , no flow etc. The lines go hard fairly quickly but its not a problem as I always replace my filters and fuel lines every Spring when I clean my carbs.
Its very reassuring to be able to see the fuel flow filling the carbs and the air venting

 

[Brassneck]

I think the letcocks are lrobably gummed up or clogged, so my question is this- am I better off replacing both petcocks or buying the rebuild kits from mikes? The rebuild kits are half the cost, but i read a little of tje petcock rebuild thread and it sounds like a hassle. Mind you I have a ‘77 without vacuum, but the polishing and all that just doesnt sound like fun to me. If new can be depended on, it would be worth it to pay twice as much for the convenience of just bolting new ones on and going.

I would spend a little time cleaning them. OEM quality is hard to beat...they are super easy to take apart and clean and BECAUSE they aren't vacuum one's, then there's really nothing to polish. Just pull them off, and get the run a pipe cleaner or the like through the various channels. Then make sure the rubber bits & seals are looking good. You may as well look in the tank and see what's in there and flush it out. A dirty tank means dirty petcocks which means clogged carbs down the road. New petcocks or old will have the same issue if your tank has crud in it.

 

[5twins]

If the rubber disc with the 4 holes in it looks a bit worn or chewed up from the lever turning against it, you can usually just flip it over. The back side is usually unused and like new. I've fixed a couple "leakers" like this. If it does need replacing, a genuine one from Yamaha is best. As you can see from the parts diagram (and as mentioned), there really isn't much to these, they're quite simple inside .....

http://www.boats.net/parts/search/Yamaha/Motorcycle/1977/XS650D/FUEL TANK XS650D/parts.html

And I also agree, original stuff is so much better made. Aftermarket petcocks in particular can be real pieces of junk.

 

[tzimmerm]

Ok, Been riding all afternoon. Rode through town 25-35, then the highway 45. Fine. Then onto the interstate. Bike wouldn’t go above 50-55 for about 1 mile. Took the highway home. On the highway, I got it up to 65-70 a couple times. I tried it in fourth since someone here in the forum asked me if I could redline it in fourth. They never explained why but I assumed it was to diagnose whether it was a fuel or electrical/timing problem. It did end up bogging down in fourth as well, but it seemed to to better than in 5th. Which brings me to this question- what should my rpm’s be at highway speed? I know the new speedo I bought from Jim works, but I’m wondering if the tach is maybe a little off? It seems like in 1st 2nd and third gear, from 5-45, I’m never above 4 grand. It idles nicely around 1.5 now that I have those fuel lines straight. The redline starts at 7.5, but I just can’t see how you would ever get it up thh high. When I was going around 65 on the highway in 4th the tach read around 3.5-4. That seems too low? Anyway, tried a couple other highway runs. It bogged down at 50 on one, then I got it up to 65 again about half an hour later on a different road. Still seems like a fuel delivery issue. I think all I can do now is check the carbs. If I take them apart to clean them, does that mean I have to sync them again?