need some help with an engine

[gonefishin485]

hey everynody, im new here and i need some help

i have a 81 xs650, and ive been having trouble with it lately and cant figure out why, im hoping someone here can help

i bought the bike last year and its always been a bit cold natured, takes a while to warm up, no biggie, its an 81

but lately the trouble ive been having, is that from an idle, you cant twist the throttle too fast or it will spit, sputter, and pop out of what sounds to me like the left pipe, stutter a few times, and then catch. it will do it regardless if your taking off in first gear, or its just sitting at an idle and not in gear. to get it to accelerate smoothly you have to roll the throttle kinda slowly and it wont spit or sputter. its just aggrevating because im use to the *wop wop* throttle on my dirt bike from a dead stop idle i can rap the throttle and take off, id like to be able to do that with my xs, i use, but i havent been able to in a long time

ive tried everything i can to fix it, but nothing has worked, the carbs are squeaky clean, their synched with a homemade manometer, it has k&n air filters, and open pipes, it has the proper matching plug caps from mikes xs, and the right plugs. other than this trouble the bike runs fine and i put many miles on it.

the ONLY other thing i thought it could be, when it was at a friends house, he was changing the charging rotor, his dogs got to it and chewed my plug wires off. he replaced the entire coil with one from a suzuki i believe, or it might have been off a yamaha 1100, im not sure, his brother gave him the coil and he changed it before giving me the bike back, all i know, is it was off a 4 cylinder bike, and it works, but could that be my trouble? or is it something else?

someone please help me, its such a good bike for it to have this stupid little quirk, and also its aggrevating at a red light to twist it just right to move. so please, someone help me

 

[BigJimmyW13]

Well welcome to the site! Any pics of the bike? Sorry I don't have an answer for you! If it were happening to me.. I'd be asking for an answer on here as well.. :-D

 

[yamaman]

G'day mate & welcome along
First of all, where in the world are you?
These bikes are notorious for charging problems, and without a fully charged battery, they will piss & fart all over the place! So you will first need to find your battery voltage, engine off, at idle & at 3000 rpm. That will give us a little more to go on!

 

[geezer]

.The first thing any new owner does is pull the airboxes off and install pods 2nd thing that goes is the muffler system why who knows i guess to be hot roddin or choppin .... bad move cuz you got bs 34 carbs they come non adjustable and set very lean from the factory.....and you have compounded the problem by opening up the pipes and filters.... good news is bs34,s are very good carbs.

If you went to the trouble of building a slack tube manometer then I willl asuume you understand the balancing procedures I wont insult you with a lecture about doing the static balancing porcedure ect

What do I think ....minus any ignition/charging ...dirty ignition and kill switch problems ie full voltage to coil is you got a dirty pilot circuit and your generally[ way to lean] did you adjust your floats?... did you check for carb boot leaks and vacuum line leaks to petcocks


Who you need to get advice from is XSJOHN he is a bs34 tuner and factory trained mechanic who makes custom adjustable needle sets

http://cgi.ebay.com/ebaymotors/XSJO...rcycles_Parts_Accessories?hash=item439daf5bcd

Take advice on this forum with a grain of salt alot of newbies on here ....

For the record I dont no shit and the older I get the less i know..
.
pamcopete
XS John
grizild1
inxs
5 twins
Mule
Roy Fisk
and a FEW others like Barb
the AUSSIES and BRITS are another reliable info source/

These are some of the people. who I know ..... knows how to trouble shoot and tune
.
do a search for the carb guide it was just posted the other day or do a search over at the 650 garage hell I will find it for you
http://www.amckayltd.com/carbguide.pdf

.

 

[xsjohn]

Was this problem there before the coil change.........I can make you a needle set to solve the carb problems......also a custom pilot and a bit larger MJ (I don't supply the Main Jets but can recommend the right size)....these are lean anyway but with pods (if that what's on it now and open pipes especially)....if you are in doubt about the coil maybe get another one off ebay or Mikesxs......80-83 coils were all the same...plug caps are 5K ont the TCI bikes......plastic floats on the 81 are set at 22mm....and are the brass plugs off of the mix screws so you can ajust the mix screws.........and did you change the plugs and what cclor are they after say 10 miles or more........NGK BP7ES or Autolite 63.....always good to clean all the wiring harness connections including the large connectors and the kill switch and use dielectric grease.......untold future proplems are eliminated there....and maybe check your timing with a light at 1200 rpm and see if its on the mark and that it is advancing when you reve it a bit (since you may have changed the rotor).......what is the compression on both sides with throttle held wide open..............xsjohn

 

[gentlemanjim]

John,

On my '83 I don't see the sealed covers over the mixing screws. Did they eliminate them that year or am I missign something?

 

[xsjohn]

All mix screws on the BS34's were sealed off as far as I know.....someone did you a favor there...xsjohn

 

[gentlemanjim]

I don't mean that they aren't sealed. I mean they aren't there.

 

[xsjohn]

I'm confused..........are these BS34's......chromed steel tops........all came with a brass plug covering the mix screws ........on the engine side of the carb.........up top.......

Below pic the plug has been removed......it's always good to put a bit of grease on the mix screw heads when you have them out..............xsjohn

 

[gentlemanjim]

I just didn't know where to look. On my previous XS650's the caps were on the side facing outward.

Thanks as always you have the answers.

 

[gonefishin485]

well, while i dont think its in the jetting, ill give it a try and hope for the best, what size main jets do you reccommend?

and for the life of me, i cant remember when it started doing this, but i believe it ran fine after the coil change.

 

[yamaman]

Mate, the easiest & first thing is to check your voltage. Also need to know what country your in, as models vary from place to place, cheers

 

[MikeGyver]

I would check the idle mixture screw as xsjohn suggested and the floats.

 

[gonefishin485]

i am in north america, south louisiana to be specific

i just got done pulling the carbs down, cleaned the piss out of them, and still, same thing

the idle mix screws are both set at 2 1/2 turns out

my voltage is fine, 12.5 to 13 volts at an idle, the rotor and regulator/rectifier was replaced a couple hundred miles ago and i havent had any trouble with charging or electrical since

besides the little stumble, the bike doesnt have any other trouble. ok well i lied, the starter gear needs to be replaced, and it doesnt like to start with the electric start when its cold and choked, but a kick or two and she pops right off, let it warm up, push in the choke, all the way and it will sit there and lope

twist the throttle just right and i can ride for a hundred miles, but i still have to twist it just right, but why?

 

[gonefishin485]

Was this problem there before the coil change.........I can make you a needle set to solve the carb problems......also a custom pilot and a bit larger MJ (I don't supply the Main Jets but can recommend the right size)....these are lean anyway but with pods (if that what's on it now and open pipes especially)....if you are in doubt about the coil maybe get another one off ebay or Mikesxs......80-83 coils were all the same...plug caps are 5K ont the TCI bikes......plastic floats on the 81 are set at 22mm....and are the brass plugs off of the mix screws so you can ajust the mix screws.........and did you change the plugs and what cclor are they after say 10 miles or more........NGK BP7ES or Autolite 63.....always good to clean all the wiring harness connections including the large connectors and the kill switch and use dielectric grease.......untold future proplems are eliminated there....and maybe check your timing with a light at 1200 rpm and see if its on the mark and that it is advancing when you reve it a bit (since you may have changed the rotor).......what is the compression on both sides with throttle held wide open..............xsjohn

as far as i can remember, it was fine after the coil change, but it has been a while, so i can remember 100% for sure
it still has the stock air boxes, but it has k&n filters
it still has the stock main jets, and if the pilots that your refering to are the small jets right next to the main jets with the rubber plug over the bottom, were gonna have trouble, i tried to pull them out to clean them and stripped the head

 

[inxs]

- oops...thats a shame, it does pay to sacrifice a screwdriver or 2 and grind the ends to fit the jets-special tools-for just this very reason

- pilot jets will give you problems in the area where you are having them

- when cleaning, did cleaning fluid come out the the 3 holes labelled TP

 

[gonefishin485]

im sure it did, i blew it out with the air compressor and every single hole was open and flowing, and i tried grinding down a screw driver to get the pilot jets out, and it just stripped the slot off the top of the jet, so i guess if i have to change them im going to have to drill them
or if someone can tell me what size drill bit to use, ill drill the pilot jet hole out

 

[gonefishin485]

also, should i take the rubber plugs that cover the pilot jets out and toss them? or should i leave them in? seems to me if the plugs werent there it might make a difference

 

[weekendrider]

It does, but not for the better. Unless someone overtightened them(the jets) chances are they are gummed up with varnish. You can try backflushing/flooding with carb cleaner the through the mix screwhole. And maybe with a small e-z out get lucky. Just eyeballin it looks like 5/64's would be the max you could drill them and then it better be dead on center.

 

[emitchum]

my bike behaves exactly the same way until it is very warm...did you get resolution?