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Discussion Starter #1
I have made a few posts trying to get my 98 450ES running and about at my wits end. Here's where I am:
1) getting good blue spark while cranking
2) carb rebuilt and ultra soaked twice, still won't fire
3) fuel coming out the fuel line and carb getting fuel
4) pulled the valve cover and lined up the T on compression stroke, valves very close to .006
5) sprayed a little fuel in the plug hole put plug back in and it popped
6) tried again and put my hand over the carb intake and blew fuel back out onto my hand with some pressure

Some have mentioned a timing issue but if the valves line up with the T mark at .006 the timing should be OK right? If timing was bad the T and valves wouldn't be correct I would think.

Have heard CDI might be bad not sure if that would allow spark but at the wrong time. I am kinda frustrated to say the least...any ideas would be appreciated, I can give more details if necessary.
 

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That sounds like a classic CDI failure — will pop initially but not run.

Are you using the service manual diagnostics?

Ok if it was me I’d pull the CDI and bake it in the oven at no more than 180F for at least two hours. Let it cool completely!!! then reinstall. Don’t rush the cool down.
 

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Discussion Starter #5
That sounds like a classic CDI failure – will pop initially but not run.

Are you using the service manual diagnostics?

Ok if it was me I’d pull the CDI and bake it in the oven at no more than 180F for at least two hours. Let it cool completely!!! then reinstall. Don’t rush the cool down.
Only way to get it to pop is putting a squirt into the plug hole. Other than that nothing even if I spray into the carb intake. I'll try to figure out how to remove, prolly have to take the front apart.
 

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That sounds like a classic CDI failure — will pop initially but not run.

Are you using the service manual diagnostics?

Ok if it was me I’d pull the CDI and bake it in the oven at no more than 180F for at least two hours. Let it cool completely!!! then reinstall. Don’t rush the cool down.
Only way to get it to pop is putting a squirt into the plug hole. Other than that nothing even if I spray into the carb intake. I'll try to figure out how to remove, prolly have to take the front apart.
CDI should be easier to remove; read the manual generally right up front
 

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CDI is housed upfront held in place by a rubber boot, plugs in on the left hand side on top of the main square frame rails. I’d remove the front fender, be a hell of a lot easier.
 

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Discussion Starter #8 (Edited)
CDI is housed upfront held in place by a rubber boot, plugs in on the left hand side on top of the main square frame rails. I’d remove the front fender, be a hell of a lot easier.
OK front fender removed to make easy access to the CDI. Oh my very dirty up there. Does it just slide out of the rubber boot or does the boot come apart? If it just slides out I will probably have to remove the connector first, don't want to stretch the wires...
 

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Just slides out of the boot, it will be stuck though with the years of crud trapped in there. Wet it with a sponge and water, always works for me.
 

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I know you have NO compression tester... but humour me...

Plug the spark plug hole and crank motor. If you have compression of any kind it should blow past your finger ect... I understand some may think I'm crazy but you can tell IF you have good or weak compression...
 

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Discussion Starter #12 (Edited)
I know you have NO compression tester... but humour me...

Plug the spark plug hole and crank motor. If you have compression of any kind it should blow past your finger ect... I understand some may think I'm crazy but you can tell IF you have good or weak compression...
I will do that tomorrow also after church , think I can handle this. many thanks for the advise....

Any way to calibrate my thumb to a psi reading??
 

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I had to take the fender off of mine yesterday yeah a muddy mess under there.
I made a bucket of hot soapy water and used a rag and bottle brush. I have a few sizes.

Try not to get the connectors wet, you can wet the rag and wipe off the connectors.

The CDI has these little connector locks that you have to pull open, then pull off the connector. Since it’s dirty might not want to come off at first so be gentle. Hit the connectors with some electrical contact cleaner and use a plumber acid brush to clean off/out the connections. Then with a clean brush apply a thin layer of permatex dielectric grease to the contacts. This will seal out water and make the CDI easier to disco.

Ok once you do that. Just plug it back in and see if just cleaning the connectors solved your problem
 

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Have you measured compression?
No wish I could, no tester or if I could borrow one no spark plug adapter..
I can imagine your frustration mate. Stick to the basics during your initial diagnosis. You're happy with the fuel supply to the carb, you have ignition, you also have a clean spark. You've checked your valve clearances but staying on that for a moment make sure the gaps are correct (not there or about) a little too much of a gap is better than no gap at all! Especially during this period of fault finding. It's quite possible as has been suggested that you may have lost compression, either due to a badly seated/burnt out valve or maybe even piston/rings/cylinder wear?
Is the oil level correct? Does it smell of fuel, another indication of potential cylinder related issues.
 

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Any fuel coming out of the exhaust? Any chance the plug wire is rubbing on something metal like part of the frame? A weak coil could fire with no load but once back in there wont be strong enough, also a pos/. Maybe i missed it, but did you try another plug?
 

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Discussion Starter #17
OK trying to answer to some of the latest posts:
1) @wheeler--put my finger over the plug hole and cranked a few times, pushed my finger off pretty strongly.
2) @Goober--got the CDI removed and connectors off and cleaned with contact cleaner, installed but still no love
3) @Chalkymon--oil level good and pretty new, no other smells
4) @ktriebol--did check valves yesterday and with T lined up on compression pretty much had .006 on both valves
5) @ATC4ever--no fuel coming out exhaust, but am getting air flow from engine
checked plug wire up to the coil, no rubbing or bare wire
yes have tried 2 plugs

I tried to get the wires off the ignition coil but they seem stuck pretty good. They should just pull off right? And yes I agree just because getting spark on the plug doesn't mean it's good.

I again tried some carb cleaner in the plug hole and it kinda pops but doesn't really run, fuel is on.
 

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The CDI should be a plastic tub with sealant. Yup lay the CDI in the oven with the sealant side up. The circuit board is laying at the base of and inside the tub.

So what you’re trying to do is drive off any moisture, perhaps relieve any sealant tension on the board. It might only last a day or maybe a year—maybe will help you prove CDI is bad.
 

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Discussion Starter #20 (Edited)
The CDI should be a plastic tub with sealant. Yup lay the CDI in the oven with the sealant side up. The circuit board is laying at the base of and inside the tub.

So what you’re trying to do is drive off any moisture, perhaps relieve any sealant tension on the board. It might only last a day or maybe a year—maybe will help you prove CDI is bad.
Got it laying on my wood stove right now, low fire going but nice and warm....

Ever tested the ignition coil? I don't think I can just use my voltmeter. Trying to get the leads off but seem stuck and don't want to get too crazy and break something. It doesn't look like there are any clips, just slide on.+
 
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