New Engine Wont Start

[ononewheel]

Hi, I have just put a new top end in my Cagiva WMX 250. I replaced the small end bearings, piston etc.

I also put a new spark plug in, new tranny oil, new air filter, carburettor jets, and upon trying to first start it it would not.

It sounds like its nearly going but just dont, also its a bitch to kick over now since I put the new engine in but i put this down to the increase in compression.


I have had it start a couple of times and as soon as i let go of the throttel it dies. Then when I start kicking it over again it wont start.

PS Have tried a different spark plug aswell.
Did not think that idle settings could be adjusted untill warmed up????? has this got anything to do with it????


Have tried cleaning the plug etc, which has helped but does not long term.

There is fuel getting to the engine, as the spark plug is wet (A sign of rich running I read?), and the spark plug is sparking as I held it up to the engine casing.


I moved the needle clip position, up one to lean it but it started for about a second then died and wont start again.

Please help.

Also when I pull the spark plug out it is a little dirty, which I think could be a very little bit of dust from the pipe, which needs running through.

Any help greatly appreciated.
After lunch today I am not on the net till tuesday, and would likle to get the bike running over the weekend so quick replys appreciated.

PS I forgot to say after eliminating nearly everything, spark, fuel etc, I though it could be the reeds, they were old but not that worn, but dirty! So I replaced with the boyeseen dual stage reeds I had which i wernt gonna put on untill a ran the engine in.

This did not make a differenece.

Also when it does kick over, sometimes it backfires, so bloody powerfull that the pipe comes off the manifold.

Luke

 

[NO HAND]

Did you remove the magneto? I once bought a broken bike and the magneto was mounted upside down. It made the bike fire when the piston is down instead of up. The bike didn't start but had big back fires like you explain. Did you try pouring a litle amount of fuel into the cylinder, from the spark plug hole, put the spark plug back and see if it starts, it will tell you in what direction you should look for problems.

 

[Captainuno]

I agree with no hand

Luke,
Check your engine timing. The setting is 1.0mm BTDC or .039 inches BTDC.
You need a dial indicator to set it right. Set the piston at TDC then rotate crank counter clockwise to -1 mm on dial indicator then align the marks on your stator to the marks on your flywheel. See attached link.
http://www.cagivawmx.com/technicalignitionmotoplattiming.html
Correct spark plug is a NGK B9.5EGV, this plug is hard to find, I use a B10EGV.
Make sure your power valve is not hitting or rubbing the piston.
Hope this helps.
Kirk

 

[rickyd]

DId you install the piston in the correct position?? There is usually an intake and exhaust side too a piston..

 

[kelsorat]

Sounds like a timing issue. Unfortunately some people suggest using a dowel rod measurement technique as a cheap alternative to the dial indicator. Forget it. Invest in the dial indicator. If after timing adjustment, bike still will not start, your ignition is toast. Check to see if PVL makes an aftermarket ignition for Cagiva. I used to ride some vintage MX, and did not see many Cagiva's, but if they are anything like a finicky Maico, then your timing better be spot on, and your ignition better be in good shape and pass resistance measurements, or you just inherited a $600 problem.

 

[ononewheel]

Hi, I have finally managed to get it started. i had to play around with the idle settings, however after the engine has been run it wont start again for like hours, and it sounds a little different.

When you pull the throttel back the bike revs up high easily, maybe to easily im not sure how to explain it but it runs just not crisp.

Need to have it running for long enough to sort the idle out.

C an keep it running for long but the exhaust note is a little different than what I think it should sound like.

Any suggestions, could it just be the idle settings need tuning in???

PS I did fit boyseen power dual stage reeds because I though it might be down to the reeds, and I had these waiting to go on soi put them on.

Could this have changed the jetting a little bit and contributed to the problem???

PS For some reason when I tip my bike to the side nop petrol comes out.

 

[ononewheel]

Checked air filter it was fine. There was some oil in the filter box so I cleaned it.

No difference.

I need help.

usually it wont start, when it does it redlinews to easy basically, I can't have that happening cos I have not even run my engine in yet.

Lol the amount of times its been started im probably up for another rebuild before I even run it in!only joking!

Please I need your help
PS Idles very high with choke on, i kinda keep moving it to keep the bike running but not idling to high.

When i turn the choke off I can keep it running with the throttel it idles high but cuts outs out.

I always have to use the choke to start.

 

[_j0kA_]

sounds like your jetting could be lean causing a high rev and surge sensation, not to mention turning the choke on richens the mix..

 

[ononewheel]

It cant be timing, did not touch it taking the top end off did not go any where near the bottom end!

You back up my thoughts of thinking that the idle needs tuning in ie idle air screw and idle rev screw.

But It is hard, because I dont want it to seize warming up as I have just put a new top end in, and yet I need it to run untill warmed up so that i can make the idle adjustment.

The only thing is though, right, say that the off running is because of idle jetting (which is what I think), why when I start it why won't it start after for a fiew hours????

is that because the jetting is off and when the engine heats up the jetting is further off???

I would have though it would be easier to start when hot if it was lean as hotter weather requires leaner jetting and colder weather requires richer jetting.

PS It does smoke like a bitch when started (running rich??) anyways im gonna keep starting it when I can and adjust the idle settings, the only thing is my right foot is startin to bruise in the middle because of stamping on the kickstarter so much.

Man, I need my bike working!!!!

 

[ononewheel]

Shold I sort the idle problem my self of just take it into a shop because I aint run the engine in yet I dont want it to seize from being lean or rich.

Responses appreciated.

Luke
PS I cant do a signiture for some reason.

 

[kelsorat]

Not sure the carb you have. Reply back with carb brand for your 88 wmx 250, your altitude and air temp and I will be able to help.

 

[ononewheel]

I have a Dellorto VHSB37AS carb with a 195 Main Pilot, a 45, I think he choke jet is a 60. The jet needle is a K50.

The temperature round here is around 28-29 at the moment.

Im not sure what the altitude is but im a way from the coast. I live in england, surrey.

the jet needle clip is one down from the top position.

For some reason when I tip the bike over to the side, and i mean right over till the peg is touching the floor nothing runs out the overflows, why is this???

PS I have just installed a new clutch cable which dont work properly for some reason.

The arm that it connects to and has a little spring on feels week, you can pull the clutch in fine with no resitance and to easy, but it wont return feels like the spring is very week.

However it worked perfectly with an old cable before I rebuilt my top end. And I did not chnage the clutch or anything to do with it.

 

[ononewheel]

Please, any help appreciated. It s sparking, petrol getting to the carb but maybe not to the engine I dont know heelp

 

[Ol'89r]

Please I need your help
PS Idles very high with choke on, i kinda keep moving it to keep the bike running but not idling to high.

When i turn the choke off I can keep it running with the throttel it idles high but cuts outs out.

I always have to use the choke to start.

ononewheel.

Sounds like a classic clogged pilot jet condition. The pilot jet and pilot air system is what controls the idle circuit on your bike. It is the little jet that sits right next to the main jet.

Remove the pilot jet the air filter boot and the air adjustment needle. Using compressed air, blow air through the pilot jet hole while holding your finger over the air adjustment needle hole. You should get air blowing out of a very small hole in the air intake side of the carb. Likewise, when you blow air into the air adjuster hole you should get air blowing out of the pilot jet hole. This entire circuit should be clean and unobstructed.

Before reinstalling the pilot jet, make sure it is not clogged. You should be able to hold it up to a light and see light through the jet. It should have a very small orfice. If it is clogged, soak it in some carb cleaner. It is not recommended that you use a wire or anything like that to open up the jet.

This is a common problem on bikes that have sat for a while or may have water or dirt in the carb float bowl. The little pilot jet is the first one to clog up.

Good luck. :cool:

Just my $ .02

 

[ononewheel]

Thanks. I will try it tonight, I will give it a good old clean then reinstall it.

Won't have any gas to test it untill tomorrow because of erm, erm, needed it for something else.

What do you mean by air adjustment needle whole, the little whole on the inside of the carburettor?

man, I just can not wait to get my bike working.

Just got to sort this dodgy clutch after this. Can fiqure whats wrong with the clutch, worked fine months ago before rebuild, i rebuilt the top end changed the cable and now it don't return.

The spring on the little lever that the clutch cable connects to by the engine seems very weak, however it must have been this weak before and the clutch worked fine???

Thanks

 

[ononewheel]

Thanks. I will try it tonight, I will give it a good old clean then reinstall it.

Won't have any gas to test it untill tomorrow because of erm, erm, needed it for something else.

What do you mean by air adjustment needle whole, the little whole on the inside of the carburettor?

PS I replaced all the jets when i rebuilt it, so it cant be "varnish" but ill clean it all because it could be as you say dirt in the tank or something.

man, I just can not wait to get my bike working.

Just got to sort this dodgy clutch after this. Can fiqure whats wrong with the clutch, worked fine months ago before rebuild, i rebuilt the top end changed the cable and now it don't return.

The spring on the little lever that the clutch cable connects to by the engine seems very weak, however it must have been this weak before and the clutch worked fine???

Thanks

 

[Ol'89r]

What do you mean by air adjustment needle whole, the little whole on the inside of the carburettor?

Thanks

ononewheel.

I'm not that familiar with the carb on your Cagiva but, on most carbs the air adjustment needle is the screw on the side of the carb that adjusts the air mixture. The other hole is a very tiny hole in the bottom of the air intake bell side of the carb. When you remove the adjuster screw and the pilot jet and blow air into any one of the holes, you should get air blowing out of the other two holes. If not, the circuit is clogged.

 

[ononewheel]

Yeah I did what you said. There was a little bit of dirt in the pilot and behind the air screw.

Just got to get some gas, and start the baby up.

I am not sure what is going on with the clutch though!

 

[Ol'89r]

Just got to sort this dodgy clutch after this. Can fiqure whats wrong with the clutch, worked fine months ago before rebuild, i rebuilt the top end changed the cable and now it don't return.

The spring on the little lever that the clutch cable connects to by the engine seems very weak, however it must have been this weak before and the clutch worked fine???

Thanks

ononewheel.

Try removing the clutch cable from the lever on the engine and make sure the lever returns by itself without the cable attached. This will eliminate the mechanism in the engine. If, the mechanism is ok, then the problem would be in the cable itself.

Make sure you have the cable routed correctly with no sharp bends or kinks in the cable and that the inner cable moves freely within the outer cable housing. Also, be sure you have a little play in the cable adjustment. You should have a little bit of free play in the clutch lever before you feel pressure against the clutch.

Good luck, hope the dirt in your pilot jet was the problem. :cool:

 

[ononewheel]

Yeah the lever on its own, the one on the engine, returns fine.
It feels a little erm, weak but returns fine.

But when I pull the lever on the engine, and put it in gear i try to turn the back wheel to check that the clutch is working and the back wheel is locked as if still in gear.

The cable is fine, brand new. Works smooth!!

PS I did not touch the clutch during top end, did not go near the clutch.

I know it is probably something simple but I just can not think what it is.

PS how do you do a signiture??

 

[Ol'89r]

But when I pull the lever on the engine, and put it in gear i try to turn the back wheel to check that the clutch is working and the back wheel is locked as if still in gear.

PS how do you do a signiture??

ononewheel.

Sounds like your clutch plates are stuck together. This is not uncommon, especially on a bike that has been sitting for a while.

There are two ways to break them loose. First, put the bike in 5th gear. Pull the clutch and rock the bike back and forth until the clutch breaks loose. Or, when you get the bike running, just put it in gear and it should break loose.

To do a signature, click on User CP at the top of the page. Then click on Edit Signature.

 

[COLEMANAPP]

Onewheel,
I have a similar bike (88 Husky wrk 125- Cagiva based bike) and I can't pull in the clutch and turn the back wheel either, unless the bike is warmed up. If your motor isn't running right, I don't think you can establish that your clutch isn't working yet by trying to turn that back tire. I had an issue with my clutch plates sticking together like Ol89'r said but my bike also sat for 10 years. See how it works after you get it running and can ride it for a while. Hope it helps.
Bob

 

[ononewheel]

Ok ill wait til I get it running to check its just that in the manual it sais that whilst pressing the clutch you can kick start in any gear which when I tried this the back wheel spins so its got to be stuck.

Well when I get it working Ill pull the clutch in and press on the gearshifter and ill either be pulling off ok if the clutch sorts itself out, or if not wheeling off or doing a rolling burnout.

:laugh:

 

[kdx633]

sounds like a low float level problem/fuel delivery problem to carb.that will cause high idle choke situation.backfire could be a result of this also as the low float creates lean mixture.check to see if petcock strainer is clear that may be causing the immediate re-start difficulty.good luck

 

[darringer]

A friend of mine with an old rm250 had the same symptoms you have. After much searching, he found that the clutch-side crank seal was leaking, drawing tranny oil into the combustion chamber, making it extremely hard to start. It smoked like crazy, and would not idle. Coincidently, the bike ran fine before he put a new top end, just weak. The bike had sat for awhile before he did the top end job. Maybe check the level in the tranny. Couldn't hurt.