very odd experience need some opinions

[hillhudson]

hey all, this is my first time posting here although i've been reading for a year or so now.

i recently finished my bobber build, the engine is a stock 1977 xs650D, the carbs are also stock bs38. i installed the pamco ignition and new coil, as well as hughs handbuilt PMA system and wired the whole thing up based off of popular diagrams that i found on this forum. the carbs were torn down cleaned and rebuilt with 150 mains and 40 pilots and i'm running pod filters and straight pips with no baffles. originally i started the bike for the first time after the build with stock jetting and it would start and idle fine but the second i would twist the throttle it would bog down very hard. so after some reading on this site i followed some advice and put in the 150 mains and 40 pilots and then started it back up and it ran great and i drove it round for about a half hour and did everything from 5 mph to 50mph and it was great. i then parked the bike in the garage and went to go start it again the next day and no go, i was all of the sudden back at the way it was acting with the stock jetting. it idles fine but bogs hard at any acceleration. cam chain adjustment looks good, valves look good, and timing in within spec and on point. I am completely stumped about how it could work one day and then not the next. i puled the plugs today and they were totally black, so i cleaned em and lowered the needles (moved the clip to the top) and it didn't help at all. any ideas here would be extremely appreciated!

thanks all

-hill

here is my bike
http://www.pipeburn.com/home/2013/12/20/1977-yamaha-xs650-escape-machine.html#.Uv7EikJdV6c

 

[angus67]

wow, man. that is a sweet bike. the early 70's front drum fits perfect. if you kept the 77 disc on it, it would look, maybe not terrible, but deffinately lacking. Is that wood on your kicker? How did it run at high rpm's when it was running good? Those pleated pods disrupt the incoming air. Unifoams are superior.
As far as the weird running, the brass pickup tube that hangs in the bowl, and the needle rides in, is held in by a small o ring. if that oring is deteriorated, gas will be pulled thru into the motor, check it.
http://www.motorcycle-superstore.co...ID=AvantLink|NA|55963_d3fe7c65&WT.MC_ID=54020
this is what most of us run.

 

[hillhudson]

angus67 thanks so much for the fast reply and the tip about the o-ring. you rock, i'll check that and get back soon!

yea that it wood on the kicker, i turned all my own metal and wood on my metal lathe, it was a cool experiment. at high rpm the bike was handling great, then the next day BOOM bog down city, pulled the carbs off and gas was soaking all over.

here is another link to my bike for better in progress photos

http://esccollective.com/escapemachine

cheers!

-hill

 

[hillhudson]

also, where would i find this o-ring if i need to replace it? can't seem to find it on mikes xs

 

[NONclow]

http://www.mikesxs.net/product/48-5020.html

 

[hillhudson]

awesome! thanks NONclow

 

[Soliddrummer]

That is an awesome bike, good job NOT using a peanut tank like everyone else. It's safe to say this is a carburetor issue, I would do a tear down, clean and rebuild again. I know it seems like overkill, but on a 30 year old set of carbs, it's not entirely uncommon to need to re clean a freshly cleaned set of carbs as running them will knock some junk loose from places that didn't get cleaned the first go round.

 

[Gene]

. at high rpm the bike was handling great, then the next day BOOM bog down city, pulled the carbs off and gas was soaking all over.

l

Do you leave your petcock open when not riding causing the bowls to over fill and soak the filters?

I too had those filters on my bike and they seemed to work fine, but then shortly after coming to this site I swapped them out for velocity stacks and that improved my bike significantly (i'm jetted accordingly to my exhaust/lack of air filter setup)

 

[hillhudson]

hey thanks soliddrummer! i'll do a re-clean and replace those o-rings for sure and report back. @Gene i haven't let the petcock stay on for very long other than that short ride and just trying to tune the thing. thanks for the heads up on that stuff

 

[hard_y_rd]

150 mains seem awfully big even for mods like you have. Stock is 122.5 for 77. 2 sizes up would put you to 127.5. I dont know how you got to 150. Maybe im missing something here.

 

[gggGary]

Yup great looking bike.
What is the inside of the tank like, what fuel lines are you using. I would suspect migration of some "non gasoline" to the float valves, enricher circuit. Could be varnish rust what ever coating that may have been used. Also do the quick dip in cup of hot water test of the floats.

 

[DogBunny]

150 mains seem awfully big even for mods like you have. Stock is 122.5 for 77. 2 sizes up would put you to 127.5. I dont know how you got to 150. Maybe im missing something here.

Your jetting is way off. It was off when you were running stock, and it is off after the re-jetting. You had a lean stumble initially, which you have now traded for a rich stumble. The 40 pilot jet size is crazy. You never mentioned the slide needle clip position. I recommend trying 1 up on the pilot to 27.5, and 4 or 5 up on the mains to 132.5 or 135. And, you should raise the needle clip up to the second slot from the top. This is all covered in the Carb Guide that is found on this sight.

Yup great looking bike.
What is the inside of the tank like, what fuel lines are you using. I would suspect migration of some "non gasoline" to the float valves, enricher circuit. Could be varnish rust what ever coating that may have been used. Also do the quick dip in cup of hot water test of the floats.

This is a lot more likely than a bad o-ring, imho. But I still think straightening out your jetting is likely all you need.

You also need to install a baffle -- you will only be able to get a very short one into the ends of your pipes, but you don't need much. Your bike will run better and be easier to tune. Home-made ones here:
http://www.xs650.com/forum/showthread.php?t=26822

 

[swbill]

Check those air filters. The rubber boot on them covers the air jets on the back of the carb. I ran those kind before and had to cut some of the boot away on the inside to get it to run right.

 

[JP50515]

I was wondering when you'd show up on this forum. Saw your bike a while back when it hit the internet. Read your story about why you built it. Very cool!

It does sound like a carb issue. Also check your float height's on the BS38's after having two of those brass floats leak, fill with gas and sink, they could no longer float high enough to shut off the gas from the lines. I do not recall the exact height off the top of my head, but it's in the carb guide. Had to get new floats for mine. If you pull them out and shake em you can hear whether or not they've got gas in them.

Had gas pouring out of them all over my engine and floor without me realizing till the next morning....ha

 

[hillhudson]

Hey thanks everybody! I really appreciate your help and opinions. I rejetted to the 150 mains and 40 pilots because i read here on this site that that was a good way to go for bs38s with pods and stright pipes. The tank is raw steel on the inside. Possible that some crap got in the carbs and clogged thigs up.

So on my list now via all of your guys awesome help is:

Check o-rings
Check fuel and
Try 27.5 pilots and 135 mains
Check floats for damage
Re-clean carbs
Check air filteds/get better ones
Drink whiskey and ponder life

 

[hard_y_rd]

I like option 7.

 

[angus67]

is it coincidence you put whiskey as #7, as in Old number 7?
I too cut some lip off those pods, then realized in order to cut enuf away, I was just basically allowing in unfiltered air. Get the uni's

 

[hillhudson]

angus67 you know it my friend. and yea, i took a look at those rubber lips on the pods yall are talking about and i see how they cover up the passage ways on the carbs, also just got those suggested jets and gunna get those uni's. oh also, emailed JBM industries to buy new diaphragms, cuz it looks like mine have small cracks and might not be sealing well.

 

[angus67]

you could try to fix those diapgrams. some have had success with a piece of latex glove on both sides, and a very small amount of rubber cement. The jbms are a good product though. im wanting carb boots. My carb boots from mikesxs are holding up, but when the time comes, JBM it is.

 

[hillhudson]

Ok guys, quick update. I recieved the 135 mains and the 27.5 pilot. I also installed jbm industries new diaphrams. Aaannddddd nothing changed on startup still gogs down really hard when the throttle is engaged at all. Oh also replaced those little o-rings too.

What next? New carbs? Kinda considering it