Another Starting Problem

Ok i just got everything back together and go to start it up and it cranks but nothing. i put some starting fluid in and it screamed like it was at full throttle and then died. tried cranking it without the starting fluid and once again it just cranks but does not start. I tried a few times and now its making a clanking sound which i'm pretty sure is the starter. i'm pretty sure i got spark since it fires up with starting fluid. what could be wrong? Plz help. by the way its an 83 seca 750r.

 

Bikes can be difficult to get started the first time after a rebuild, check the basics, fuel flow & spark, I jump from a car battery so you get a fast spin AND a good spark.

 

Check to see if you're getting fuel through the carbs and into the cylinders (on the plugs). If not, check the enrichener (choke) circuits in the carbs.

 

thx guys. i think i will give the carbs a good cleaning and see what that does. its just weird that it only fires up with starting fluid.

 

I'm confused, you put it all back together without cleanig & bench syncing the carbs ?

 

it only fires up with starting fluid because it's not getting any gas.

least you know it's getting spark.

 

Hi, I've been having similar problems with my XJ.
They seem to be a bugger to start when the carbs have been off - even if they're set up right.
The idle adjuster screw is mucho-sensitive and can cause probs if a long way out.
My bike is (kind of) running again now, but not without issues.
See my threads ("Choke Circuit Diagram" and "It Runs") for a list of symptoms and for much related help and advice from fellow XJ-ers

Nige

 

And float levels?

Is this bike "modded" are you running pods, or no airbox, or any intake mods?

 

I read your other thread(project cheap racer) where you've recently cut, painted and rebuilt your bike. In that thread you had mentioned that the bike ran. I'm not sure is that was before or after you had sprayed it with the carbs still in place. I'm guessing that you're sharp enough to have covered the intakes but the carbs looked like you had sprayed them from the sides since the insides(facing inward) of the carbs were still silver. If you hadn't covered the intakes....well, you might be in for a world of hurt trying to get it out.

Then you attacked the wiring! Any chance that you may have cut, discarded one of the swiches such as a kick stand switch or kill switch? Granted, is you had, it shouldn't fire or start on starting fluid(use wd 40 for that, it won't scar your cylinder walls and it fires almost as easily). Maybe you got some spray paint where it shouldn't be? I'm guessing that only because it ran before, now it doesn't.

jeff

 

I did mask off the intake whole before spraying it but I sprayed them while still on the engine. I took them off to remove the airbox but I didnt take the carbs off the rack so I assumed they wouldn't need to be bench synced or anything. I running an open-air filter (basically screen over a foam filter) (pics just show the screen). I'm pretty sure I would have to make some idle adjustments but I figure it would start. I tripled checked to make sure I didnt miss a thing with the wiring. I bypassed the side stand switch but made sure to leave the neutral switch alone (safety first). The more I think about it the problem has to be in the carbs. I'm going to clean sync and try to tune things when I get off work today (time permitting). Thanks guys for the help

 

Oh, the problem's in the carbs all right. You're also about to discover that trying to run CV's "wide open" presents a real challenge. They virtually won't work AT ALL if not pretty close to being sync'ed; and you face some jetting and tuning to get it anywhere near running.

The simple fact of the matter is that CV carbs were not designed to run with an unlimited, unrestricted air supply. They need a finite amount of air in order to generate the proper intake velocities to function correctly.

 

Should I just restrict the air going into the lil opening at the top of the intake (I saw that in a thread on here somewhere)? Do I still need to sync them if I never took them off the rack to start with? I'm very new to this. Any help is greatly appreciated and thx for all the help so far.

 

There is only one thing to say: do the carbs job. Off with it and do all the cleaning and then it hopefully will run like a dream. You can find a lot of description on this site.

 

Yup, block off 3/4's of your intakes and see what happens. I didn't know you had modded the box.

Personally, I hate CV carbs. I have since they first became the norm on our bikes many years ago. They don't allow us to run as much air as possible or we'll never get the pistons to rise in them. I've often wondered about switching to a set of 28- 30mm VM miks and seeing what happens on the bigger engines. Can't be any worse then these things....ok, rant over.

good luck

jeff

 

they get the job done. what more do you want.

problem is. everyone trying to beef up there performance on a 30 year old bike that just don't have the capabilities anymore.

if i remember right. top speed was only 105. which put the tach right around redline.

there's a terminology called over carburating. introducing more air/fuel then the motor was designed for. end results being engine bogging down.

 

The real problem is in not realizing that if the bike were put back in stock trim, properly repaired, renewed and tuned, it would run 300% better than what it was. These things, even the 550s, running the way they should, don't really need "improving" except for brakes and tires, etc.

The problem with CV carbs is best described like water coming out of a garden hose. With the end of the hose simply open, and the water on as full as it can be, there's still no real pressure or serious velocity. Water just dollops out of the hose.

Now what happens when we put our thumb over the end of the hose, and create a concentrated stream? The "restricted" stream has pressure AND velocity that isn't there without blocking the end of the hose.

The airbox is like puttng your thumb over the end of the hose; no filters, no stacks, not even pods is like just letting the hose run. No pressure, no velocity. CV carbs weren't designed to work that way-- so they don't.

One thing that may help, AFTER you get the carbs cleaned, bench sync'ed, float levels checked, etc., would be to clamp the rubber airbox-to-carb tubes back on the carbs to act as velocity stacks. Even that is better than trying to get them to work wide open. You might be able to start the bike.

 

thx for the info. i'm going to tackle this as soon as i get off work. been reading up on bench sync'ing so hopefully i dont screw that up.

 

if you do the hose on the back of the carb trick take a rag fold it over put it over the hose and put a rubber band around it this gives you a little restriction like an air cleaner would. Old trick but it does work

 

Well if you havent already read in my other thread (project cheap racer), I got her to fire up. cleaned the carbs and put a piece of thick filter foam in the small hole on the intake and it worked. going to take her out tomorrow for a shake down run. she idles good and revs smoothly so i'm eager to see how she performs on the road. I will keep you guys informed. thx again for all the help and info.

 

i would think that a restriction would actually be created. afterall, the air going through that hole is what raises the throttle. the more aire going through. the more it raises.

 

from what i have been reading my understanding on these cv carbs is that it needs a lil restriction to even out the air flow so that it will open the piston. so my thought was to even the air flow with the filter foam so that its a lil smoother and allows a vacum to be created. im still learning but it seems to work (at least it got it started). going for my first ride in the morning and will see how she runs and make adjustments if needed from there. im just happy to have her running (wife is to . she was ready to castrate me if it didnt fire up. she showed me the knife 8O :!: )

 

I coulda swore there was a lot of SAND in Arizona.

How exactly do you plan to keep it OUT of your 25+ year old motor?

Ride through a couple of good "dust devils" at 60mph with open carbs and you'll be wondering where your compression went.

 

yeah i'm going to get some better filter material or some dust socks. right now its nice out. winter time is great around here. low dust and no dust devils right now lol. but it is a problem i will address. thx