Author Topic: helping a friend 87 build (Read 3349 times)

punk rock kiel · « **on:** December 07, 2013, 02:18:44 PM »

I been looking around and reading up on what I could find but now my friend is at a point where I need to ask for help.

hes got an 87 long rod motor and someone had rebuilt the whole motor with hot rods crank and new piston but caught a ring putting it in and it trashed the piston and cylinder. he got it bored to 66.75 and put in a wiseco piston.

with the cylinder bolted down and head put on with the old .050 gasket, his squish is .110. the piston is .085 down in the hold from the deck.

question is how do we get his squish down to the .040 to .060 range? I assume cutting the head too much raises your compression and puts you in race gas area. So do you cut the top of the cylinder? I read you can just use the single thin layer of headgasket (.010) also but that still doesn't get us close.

2nd question. hes got a mikuni 38mm carb off his tecate 250 he is thinking of using. its got a round slide instead of flat. is this a good carb to swap out for the stock one? he thinks the jetting would be about the same as he had on the tecate unless someone else got a better opinion.

thanx for help, im usually on trx450r.org

rk88r · « **Reply #1 on:** December 07, 2013, 02:46:57 PM »

Try peeling off one thin layer of the head gasket and using that. I've used that a lot on a stock bore and one over bore with good pump gas. I believe the thin layer is about .010 thick.

rk88r · « **Reply #2 on:** December 07, 2013, 02:50:23 PM »

Fyi that was on engines with a stock head.

punk rock kiel · « **Reply #3 on:** December 07, 2013, 05:46:25 PM »

checking squish with no headgasket left me around .085 which is still too high to get the right squish and wont get the best compression

punk rock kiel · « **Reply #4 on:** December 10, 2013, 09:10:37 PM »

any help?

Pumashine · « **Reply #5 on:** December 11, 2013, 09:20:29 AM »

OEM base gasket is at .030" You can go thinner from there. I believe I have some .018 or .012 in my gasket stock. That will get you a little closer.

jamieg45 · « **Reply #6 on:** December 11, 2013, 09:36:47 AM »

Question is does the motor have a spacer plate and then the wrong piston was ordered. If so take out the spacer plate under the cylinder and then check squish.

punk rock kiel · « **Reply #7 on:** December 11, 2013, 06:08:04 PM »

no spacer plate and the correct piston was ordered. this is why I don't understand. the thin part of the stock head gasket split into 3 pieces of .010. that wont get us any closer.

punk rock kiel · « **Reply #8 on:** December 11, 2013, 07:05:32 PM »

wiseco says 562m06675 and he got one off ebay that is 562p3 for 87-89 atc/trx prolite....whats the 562p3 piston???

punk rock kiel · « **Reply #9 on:** December 11, 2013, 07:16:03 PM »

I googled it and the part number is just an older number but the same piston. if it was short rod id be a lot deeper in the hole or vice versa sticking up past the deck. could the cylinder be wrong? the piston sitting .085 in the hole is whats gonna stop from getting squish anywhere close to .060 or better.

jfwyatt1 · « **Reply #10 on:** December 11, 2013, 09:12:02 PM »

what base gasket did you use ive seen some of the cheap off brand ones that were almost twice as thick as an oem honda. its just a thought but might check that

punk rock kiel · « **Reply #11 on:** December 12, 2013, 04:23:43 PM »

ill have him check tonight but it would be almost a 1/16th thick....

Pumashine · « **Reply #12 on:** December 12, 2013, 05:23:35 PM »

Quote from: punk rock kiel;19320

with the cylinder bolted down and head put on with the old .050 gasket, his squish is .110. the piston is .085 down in the hold from the deck.

question is how do we get his squish down to the .040 to .060 range?

Go to .020" base gasket with cut out .030"............you said you have .050"
Go to .010" head gasket will cut out .030"............ 3 layer stock gasket is .040"
So you got .110" - .060" now you have .050" ..........squish Problem solved