Revs straight up whenever started

Hey Jimmy, when posting problems, we need some more detail than that! You need to post at least the year & any mods of the bike in question! Also a better dicription of how it revs, how high will help. :cheers:

Possible problems:
Advance stuck on full?
Leaking manifolds/vacuum?
Cable shagged?
 
Sorry man I was just frustrated as hell whenever it kept doing it. I have dellorto phf36 carbs - brand new. The I have adjusted the idle screw till I was blue in the face. It revs STRAIGHT up to the top. I am not running a vacuum petcock. I don't see any leaking from the manifolds. The cable feels like it moves pretty easily, but I guess I can't be too sure.
 
Ok, how brand new? Jetted right? Was everything ok till you swapped carbs? Has it run properly with those carbs? Tell us the whole story brother, we can help!
Does sound like a vacuum issue........
 
Out of the box? lol straight from Mikes

It ran fine before I disassembled everything to do a hardtail and change everything, but other than starting it up to know that it was alive it hasn't ran more tan 3 seconds.

Well there are some little barbs on the carbs, but the intakes are custom without vacuum barbs.

At this point I have taken them off for the 3rd time to make sure that everything was lined up internally and that the cable wasn't snagged.

Btw, I don't mean to be short or to seem like I'm dragging my feet on information. I'm just going back and forth between the carbs, orange cleaner and the computer.
 
Hi All, First post, so forgive me if I am stating the obvious, or rediculious.
I don't know delortos but if the slide is in backwards it will go flat out only.
This can be fun if you had trouble starting it and decided to jump start it!!
cheers
xstim
 
Hey Tim,

Firstly, Welcome to the conglomeration of xs owners and DIY-ers.

To answer your reply, up until after this problem I have never disassembled the carbs... Although I will tell you that it starts up incredibly fast.
 
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About 35 years ago, I had my motocross bike carb of and on a bunch of times trying to get things just right and then one time I put the slide in wrong way around. Had to jump start it down an ever increasingly steep hill.
Bike and body did recover. I was much younger. The thought of it still brings chuckles to all that witnessed it.

If only one carb is backwards it will start easier but still be one speed, flat out. Maybe someone at the factory had their own chuckle.
I'll try to shorten my posts.
Cheers
 
Well, I know nothing of the Dellortos.....To state the obvious, if it's reving high, it's either getting to much fuel or air or both. So does Mike give a initial setting for air screws etc? Are the slides fully closed? Did they come with some alternate jets? Jet needles? Air filters??
I'll be on & off for a while & will help if I can, just need to know what your looking at!
:cheers:
 
They are set up for the 650, but unsure about initial air screw settings. They did not come with alternate jets, needles or air filters. I definitely screwed with the idle screw way too long.
 
Did it run fine with whatever carbs you had on there before? What year is the bike or what ignition are you using?
 
Hey Jimmy, I also don't know anything about the Dellortos but on the mikuni carbs there are several holes in the back of the carb( near the air filter) and you can hold the diaphragm slide up and then plug the holes with your finger and if the slide falls down slowly then you know its working properly.
I would imagine the dellortos are set up somewhat similarly... you could try that out to see if your slides are workin okay?

just a thought....

.cheftay
 
Yes sir it did. It was a 1980 Special II and I am running a permanent mag conversion with Pamco.

Well I have the carbs off still and I turned one of them over and gas came running out the barb that I'm talking about so I really am beginning to think it is the source of the problem. Should I put a tube from barb to barb on the carbs or should I just block them off?
 
So it's definitely a fuel problem (or something related to the carbs or intake). What are the throttle cables and choke like on those? Anything weird there?
 
Well the golden rule for correct jetting, is there is no rule!
Slides need to be fully closed (or very nearly) with a closed throttle (cable adjustment-sync)
Carbs need to be roughly syncronised. With a closed throttle, use a piece of paper or thin card to measure any gap under the slide, then find a thicker piece that wont fit.
Now on the other carb make sure they are the same.
 
Yes hook both barbs together (or seperate), could be sucking air there!
Choke on or off?
 
Choke is off.




Here is a pic of the barbs that I'm talking about.

For purpose of figuring it out and that it is 12.15AM here I can't just go to autozone right now. So I am rigging up some caps from erasers... Yes I know, but it will bug the crap out of me if I don't figure it out.
 
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Ok, you got a car parked there? rip off the wiper washer hose & see if that fits the barb!
Or a vacuum line off the car might do????
 

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