79 Spitfire - No Power

Hawkeye · Post by **Hawkeye** » Wed Mar 18, 2009 3:58 pm

Ok, I have reached a new level of frustration and am now pleading for some help. Specifically, I hope to find someone in Southern WI or NE IA or even No. IL (I live near Racine, my folks live in IA and I have property in Neshkoro, WI - near Horicon or at least Horicon is on the way, so I will travel to a lot of places for help...) that has a good running Spitfire that I could swap a known good CDI and carb to further dial in on what the issue might be.

My story; I have posted various parts on here before which the suggestions have gotten me this far. So sled came home for Christmas ran great for two days. Third day went to try it and it would start and idle but as soon as you gave it throttle it would bog and sound like it was running on 1 cylinder. That is still the issue I have today. Now for the "this is what I have done" section...

The engine has been torn all the way down. All gaskets, seals and rings have been replaced. It has great compression (and it started again after all this work - amazing...)! I have also replaced the Stator, the CDI and the coils. The carburator (Mikuni Butterfly) has been cleaned 3 or 4 times - its good and clean. Not to mention that I have purchased a carb from a 78 Spitfire (cause its the more traditional Mikuni Slide carb) and also a Mikuni slider from a 80 Jag3000. All three carbs exhibit the same running symptoms - starts and idles great, as soon as you apply power it bogs. Finally, I have replaced all fuel lines and filters from the pickup in the tank all the way to the carb. I replaced the pumper line and also rebuilt the fuel tank (is there anything left???). This seemed to eliminate the large air bubble(s) that I was getting between the fuel pump and the carb, although now it looks like it has lots of tiny bubbles (similar to freshly poured Guiness). Also when it bogs you get a significant amount of fuel blowing back through the carb as you apply throttle. When I take the carb apart to re-clean, the bowl is always full of fuel so, I don't believe it is a fuel delivery. Oh and I have also throughly cleared the exhaust.

My current thinking is either that the new CDI was actually bad (thats why I would like to find a CDI to swap) or all three carbs are somehow all goofed up (so I would like to find one of those to try as well). I know its late in the year so if you don't happen to read this until fall of 2009, please try me then too, cause I may still be looking for answers. Although if I get the answer I will be sure to post. Thanks in advance for any help anyone could provide.

tmartin · Post by **tmartin** » Thu Mar 19, 2009 11:41 am

Does it ever pull through the bog or does it just bog out and die? What kind of rpms is this happening at? If you havent tried it already which im sure you have, prop up the track and see if you can get it to clean out.

Hawkeye · Post by **Hawkeye** » Thu Mar 19, 2009 12:39 pm

No it never pulls through / clean out. It also doesn't kill it either. Maybe bog is the wrong term. No tach installed, but I would guess it idles around 800 to 1000 RPM at idle and then when you hit the throttle it probably drops 200 rpm and starts spitting fuel back out the intake side (airbox) of the carb. This happens whether you hit the throttle hard or try to ease out it past idle. Thats the thing, it starts really easy and idles great, its just when you try to add power.

tmartin · Post by **tmartin** » Thu Mar 19, 2009 1:35 pm

If the timing was off I dont think it would idle good or start well either. i would make certain there is no obstructions in the Exhaust. It seems odd that you can change all these ignition and carb things and it doesnt affect the way it runs. I'm at a loss. I would say disconnect the exhaust pipe and try it for just a second but I know that it is not good for the motor or your ears. Wish I could be of more help.

Travis

Hawkeye · Post by **Hawkeye** » Thu Mar 19, 2009 2:29 pm

Travis, thanks. Yep I guess, I forgot to clarify that point too, the exhaust is clear as well. You can see through the Y pipe and Exaust Pipe and when I hook my shop vac up to the can, I get suction through the can just like if I put my hand over the hose. Perhaps the new CDI I got was actually bad. Before I go ordering a new one, I am hoping I can find someone who has a known good one that I can use to try to confirm that the one (new) on there is bad. You probably are starting to see how frustrating this is. Oh well all I can do it grin and bear it, I guess thats the fun part of vintage sleds...

JDT · Post by **JDT** » Thu Mar 19, 2009 10:43 pm

CDI's seam to be a problem that is somewhat common with the symptoms you have stated.

Hawkeye · Post by **Hawkeye** » Mon Mar 23, 2009 11:31 am

So did some more diagnostic testing over the weekend. After trying a fourth carb (this one a Kienhan 34mm Flat Side) and having no success we decided it had to be electrical. Some timing testing leads me to believe this is probably a CDI issue. When it starts you see the timing at about 20 degrees advanced, as the RPM's build it goes to somewhere between 30 and 40 degrees advanced and then the timing just goes completely somewhere else, way off the scale. So if I look at the stator, I really have only about 5 to 10 degrees of adjustability. So my conclusion is that I either have the wrong CDI or the new one I purchased was bad out of the box.

If I were to package my CDI's up and send them to someone would anyone be willing to test them on there sled? This would confirm my suspicions. Send me a PM if you are willing.

Meanwhile I am going to call Pats Small Engine, where I got the CDI and see if they can confirm that they sent the right CDI.

Spitfire79 · Post by **Spitfire79** » Thu Mar 26, 2009 4:04 pm

More than likely its the CDI. I have a bad one on my desk right now. I have had that happen exactly as you describe. Replace the CDI and all is well. I have had the stator go bad as well, but its usually the CDI.
Rodimus Prime used to post on here and said that they are rebuildable. I have the schematic for it if you want to try. You need to boil the CDI in solvent to soften the sealant on the back of the case

Jeff

Hawkeye · Post by **Hawkeye** » Mon Mar 30, 2009 9:27 pm

Yikes, thats some crazy stuff - boiling in solvent to open it up! I think I will just order a new one. Sent you a PM...

Thanks,
Steve

traildeere · Post by **traildeere** » Mon Mar 30, 2009 9:56 pm

I picked up a cheap spitfire for parts, but decided to try to run it.
Long story short I had the same (ish) symptoms.
It would start, but that was about it. More gas just made it worse
but then it completly quit & was tough to start.
New CDI & it runs just great.
Just my story.

Spitfire79 · Post by **Spitfire79** » Tue Mar 31, 2009 1:19 pm

Got your PM and replied
Sometimes the stator acts up and creates a similar thing. I've never tried the aftermarket cdi
The boiling in solvent part does seem scary. I was told this by Rodimus Prime ( who used to post here) some time ago but have never ried t

Jeff

Hawkeye · Post by **Hawkeye** » Thu Apr 09, 2009 5:20 pm

Wooo Hoooo! It runs, it runs!

I ordered a new CDI, this one a SnowStuff version. Installed it, and it fired up on the second pull, gave it gas and it pulled strong all through the entire throttle range. Man it runs good now (and it should cause almost everything is new). Anyway lesson learned don't buy the Kimpex CDI for the 78 or 79 Spitty, something is not right with them.

Thanks everybody for all your help, advice and being patient. I know I have been a pain. This is a great site and now I look forward to enjoying the ahh, er, I mean watching the kids enjoy the Spitfire.

When is it going to snow???