Jug spacer plate.

[Nightbiker07]

ok, heres an oddity.

my stock jug has a spacer plate between it and the bottom end.
i am running a STOCK crank, and a STOCK rod.
if i put the jug on without the spacer, the piston pops out of the top of the jug about 4mm (the thickness of the spacer), causing the piston to crash into the head.

bottom line is that it NEEDS the spacer plate.
spacer plate is NOT purchased, it is homemade, as the craftsmanship is not good quality.

i am asking possibilities of why it needs it. heres what i came up with:
1. Bottom end has been milled, but it still has factory dimples in the surface.
2. bottom of jug has been milled, but again, does not appear to be molested.
3. Top of jug has been milled. not molested, but it doesn't look quite right to me.

i am hoping the cases have not been milled, because then i will have to use this ridiculous plate when i install my 300 kit.

[NINJA]

Nobody would do that unless it had a longrod. Sounds like you have a stroker on your hands.

[SYKO]

Nobody would do that unless it had a longrod. Sounds like you have a stroker on your hands.



I second that, not to many old school air cooled strokers out there, your knock that you described could be becouse of the stroker are you running 2 base gaskets? it may not have enough clearance.

[NINJA]

Good call Syko. I didn't think of that.

[Nightbiker07]

well its not a stroker. i promise.
i put a stock crank in it, from JSWINEHART, and bought a new stock vesrah rod kit.
i could understand if i jad just replaces the rod and the crank was stroked, or if i replaced the crank and the rod was longer, but i replaced both of them.

i know for a fact that the crank is now stock, and getting another rod NEW and it being the wrong part, but the proper size for the homemade spacer are very VERY slim.
stroker crossed my mind when i took it apart for the first time, but after seeing that piston pop out with stock crank and rod ruled that out in my mind.

[Nightbiker07]

and the knock isnt it crashing into the head, it doesnt start knocking until it runs. kicking it without the plug AND dragging it down the road without the plug produce no knock.

[SYKO]

ok what? all stock and dosnt work...... im baffled... you need to show us some detailed pics man something isnt right, do you have another 250 cyl to compare 2 to? im thinking possibly in someones infinate wisdom that the cylinder could be shaved? wtf?

[Nightbiker07]

that, and if it was crashing, the piston and head would show contact signs, which nor show any of.

[Tri-ZNate]

yep need pics

[Nightbiker07]

i dont have the ability to put up pics anytime soon :( . i do not have another stock jug to compare to either.
but even then, pics would not show a 4mm difference if it was shaved somewhere.

[NINJA]

Yeah, we're gonna need to see some pics now so we can help you out.

[KASEY]

pretty simple solution,,, measure the stroke,,,,,,,,, measure the old rod and the new one.. compare the two cranks,,,,,,,

[NINJA]

eeeerrrrrrrrrrrrrrrrrrrrr not, you posted before me.

[Nightbiker07]

well, that solution is not so simple. with the old crank/rod and the new stock crank, rod it has the same problem. this can only mean that the old balanced crank/rod combo have the same stroke as the stock crank/rod combo.

as i said before, the parts do not look molested, nor show swirls from a milling cutter.

pics wouldnt show such a small discrepancy. the case appears to be fine when i compare it to my other bottom end i aquired off ebay.

FORGOT TO MENTION THIS, but i compared the rod/crank to the one in the bottom end i got on ebay. appear to be exactly the same (yes, measured, same sizes lol)

the jug is 30 minutes away, and i have to borrow a camera to get pics :(

[Vealmonkey]

Usually strokercranks have shortened rods. You can usually tell a stroker rod by the fact it has been heated in the middle and actually squeezed together to shorten the rod. As far as the piston being taller than the cylinder, you would have to show a picture. A high compression piston will usually have the dome sitting farther up than the cylinder. If the flat sides are not above the cylinder and the dome is, you may have a high or higher compression pitson. On the piston itself, does it look like the piston is contacting the spark plug? Maybe you have the wrong heat range spark plug or the wrong spark plug period. Maybe you have a piston from a different machine. Pictures would definitely help.

[Nightbiker07]

no. the sides of the piston extend past the cylinder the thickness of the spacer. it is NOT the dome extending past the cylinder.

the spark plug is pretty sure correct, NGKbr9es or something like that.

[Nightbiker07]

and the rod has not been modded like that, its smooth, one color, not molested in any way. (new VESRAH stock rod kit)

[Billy Golightly]

Is this an OEM piston? Thats the only difference I can think of. something with a different wristpin location

[bigreddaddy]

I would definitely check on that spark plug, but it seems you would have seen something on the piston when you took it apart.

[Nightbiker07]

no, i believe it is a wiseco piston.
this is a possibility i never thought of.

it does not really matter unless the bottom end was milled. it is getting a 300 jug,piston, etc. etc.

hoping i wont have to use that stupid plate...............
just thought everyone would like to hear about a really stupid problem.

[brapp]

anothe roption is i ahve seen a shaved vylinder and a shorter rod to gainmore rpm's and make it a smaller bore and if you take 4mmof fodf a bor eit woudl possibly make it down to a 200or so i am nto sure abotu this btu coudl it be a possibility?

[NINJA]

Usually strokercranks have shortened rods. You can usually tell a stroker rod by the fact it has been heated in the middle and actually squeezed together to shorten the rod. As far as the piston being taller than the cylinder, you would have to show a picture. A high compression piston will usually have the dome sitting farther up than the cylinder. If the flat sides are not above the cylinder and the dome is, you may have a high or higher compression pitson. On the piston itself, does it look like the piston is contacting the spark plug? Maybe you have the wrong heat range spark plug or the wrong spark plug period. Maybe you have a piston from a different machine. Pictures would definitely help.

Actually there are quite a few stroker cranks with longer rods also. As far as high comp pistons for 2 strokes? :crazy: That's why people get their heads shaved or run thinner head gaskets. If his piston were hitting his plug, he'd lose spark right away and it wouldn't run.

[NINJA]

Brapp are you drunk? I can't even read your post man!

[Dirtcrasher]

Nah, he ain't drunk. Somebody said he has webbed fingers or something....

4mm is just under 3/16th of an inch. You need some machinist tools and some stock parts to figure out whats up. Pretty easy to get actual strokes and distances with V blocks and a caliper would be good enough for a 4mm difference.

[cr480r]

Has the cylinder been ported to match? With the spacer on does the piston travel downward far enough to be flush with bottom of the ports? Both a +4mm rod or a +8mm crank would be obvious to the naked eye when compared to stock.... My guesses are: 1. the cylinder has been milled and spaced up to alter port timing... 2. you have the wrong piston...

[Nightbiker07]

well, it has NEW STOCK rod. i seriously doubt they sent me the wrong one, and it just happened to match the old one.

i am going to have to think the cylinder was milled, as the case looks fine, and it has a 100% stock bottom end. i will know for sure when i put the 300 kit on. if that goes smoothly, it will mean the cylinder was screwed with.

[tyman]

ok correct me if i'm wrong... maybe its just fourstrokes... but.... piston "wobble" or something would cause knocking.. i forget what they call it.. but when the piston doesn't go straight up and down, but it goes to the side a little, causing knocking on the side of the cylinder.....

just a thought......

[Nightbiker07]

yeah, we have determined that the noise is Piston Slap :O

[SYKO]

well my 300 was running with half a piston and it had some serious piston slap happening, you can tell it more on deceleration more than any other time, get that tighter top end on there to help that out.

[Rustytinhorn]

This thread isn't too old, but if its not the piston, then it sounds like the cylinder itself was shaved to possibly alter the port timing.

[300rman]

This thread isn't too old, but if its not the piston, then it sounds like the cylinder itself was shaved to possibly alter the port timing.

oops, forgot to conclude this thread......

yes, it seems the cylinder was milled, as when i put the 300 top end on, i had to have the jug cut down due to using a wiseco piston instead of the OEM one.

runs great, but i already tore the top end back apart and sent it out to get ported lmao.

i think when they cut the jug, it altered the port timing, because the 250 topend had way more power than the 300 did.........hoping the porting helps, i also mentioned to the guy that the jug had been milled and to consider that when porting the jug.
he said he got it all worked out, so hopefully it will pull the tire off the ground when i hit second gear again..........

[Rustytinhorn]

Which end of the cylinder was milled then? Was it the top so the ports would be raised higher?

[300rman]

Which end of the cylinder was milled then? Was it the top so the ports would be raised higher?

i do not know. havent measured it out against another jug.
its the only possible option though, as the new topend is fine. no spacer!

[thomasbynum]

Where did you find the 300 kit?

[BigReds Forever]

My guess is that, at some time, that motor had a different crank or rod in it, and then someone wanted to put it back to stock, and made that plate to go back to stock components.

[200x newby]

when you get the cylinder milled i talked to the guy that sells the wiesco piston kits for the 300 he said you have the mill the bottom of the cylinder not the top.