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-   -   89 EC25 3pg rebuild questions (https://www.buggiesgonewild.com/showthread.php?t=101207)

Bikertrash00 12-06-2014 10:56 AM

89 EC25 3pg rebuild questions
Hello everybody! I am a noob to the forum and gas carts but work on Harley's, Hot Rods etc, have not done a 2 stroke since high school. I actually have an electric marathon that I have owned for 10yrs and as it became time to change the batteries again I thought I would start looking for a beater gas marathon and swap all the good parts off my electric. Found the 89 I am now working on, did not run when purchase and only had 80lbs compression, owner claimed he did the top end about 5yrs ago.

I pulled the engine and top end, it did have STD piston with scratches on it and the cylinder, checked the rod bearings with no up and down movement but the wrist pin and needle bearing seemed loose in the rod, being the crank bearing feels good and low budget I do not want to split the cases, do you think it is just the pin and needle bearings?

Took the cylinder and head to my buddy at the local speed shop for machining, should I play it safe and just take .025 off the head?

Taking the muffler to another friend for welding, should I create extra work and price by having him put a larger tailpipe on....maybe double the diameter.

Thanks, Scott

TheGDFP 12-06-2014 01:43 PM

Re: 89 EC25 3pg rebuild questions
It looks like most guys just swap on a new aftermarket jug & slug, rather than bore. I'd rather have a precision bore job done here than in some 3rd-world sweatshop.

Being a REAL mild 2-stroke, performance increases are easy.

.025 off the head should be fine. I cut .060, the whole lip, to get the quench right.

You could add base gasket thickness, take the same amount off the top of the jug, raising the ports. Drop the intake floor a couple MM to open that up. Better reeds will add power.

Bikertrash00 12-06-2014 05:35 PM

Re: 89 EC25 3pg rebuild questions
Thanks for the reply, I think I might have to split the cases! Grabbed the clutch with the engine anchored and there is a little movement.

Bikertrash00 12-07-2014 12:13 PM

Re: 89 EC25 3pg rebuild questions
My cheap *** does not want to split the cases, I think being the rod feels good I will just change the crank seals and go with it, somebody chime in and call me an idiot if needed, im a big boy and will not be offended.

sccowboy 12-07-2014 09:25 PM

Re: 89 EC25 3pg rebuild questions
Crank seals are cheap enough that if doesn't work, you aren't out that much.

redcloud 12-07-2014 10:09 PM

Re: 89 EC25 3pg rebuild questions
If your rod moves sloppy side to side you would be better to go with a long block. They come with new jug, crank w rod, piston, seals and bearings and gaskets. May just as well know what you have and be done with it.
Increasing tail pipe size from the muffler may hurt the performance as they run very strick on back pressure.
Not a big deal splitting the case as along as you make sure you have removed all the bolts. Double check before pressing to split.
My advice as this engine is a bit of pain to remove and doing it more than once by hoping it will be ok is just adding work and it may fail way out in the boondocks as they never fail next to your shop.
That would be my advice.

TheGDFP 12-08-2014 07:57 AM

Re: 89 EC25 3pg rebuild questions
Splitting the cases is free, if it's already out and the top off.
Main bearings are cheap and a common item.
Rod is supposed to have a lot of side clearance at crank end, it's guided by piston and the spacers on the top end pin. It may just be a worn wristpin, easy to measure or slide so the part that normally rides in the piston, is in the bearing area, and wiggle up and down.

I'm not a fan of the drastically lean oil ratios these call for. Oil migration in a low-rev engine allows lean ratios, but I think they'd live longer with twice the oil, especially if hotrodded.

Bikertrash00 12-08-2014 09:27 AM

Re: 89 EC25 3pg rebuild questions
The wrist pin shows some bluing due to heat and was tight in the piston, there were no spacers for needle bearings and they slid freely on pin and rod exposing needles if slid back and forth. rod bearing feels good up & down, has typical side to side movement. I am also hanging up on the crankshaft, whole assembly rotates smooth but there is a little up/down side to side movement, tic/tock sound. Probably have to wait till after Christmas and see how much money I "don't" have left. If I decide to by the whole long block kit I see prices range and would assume all are made in India, what retailer would be suggested or not from experience.

Thanks again,

TheGDFP 12-08-2014 10:24 AM

Re: 89 EC25 3pg rebuild questions
I'll see if I can find a rod kit to rebuild the stockers. Better parts and my partner does a couple hundred cranks a year. I'm almost certain it's the same kit as the Polaris, around $80 for a Japanese kit, $50 for press and true. I forgot the 3PG doesn't have the spacers on the pin.

Dave Box 12-08-2014 11:34 AM

Re: 89 EC25 3pg rebuild questions
With regard to post #4, if you can feel movement when lifting the clutch then the main bearings are shot. New crankshaft seals will last about 5 nano seconds before they are ripped to shreds. To replace the seals you are going to have to pull the engine and really splitting the crankcase isn't a big deal. I would not (as invited) call you an idiot but......... replace the bearings now or repent tomorrow.


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