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Discussion Starter · #1 ·
I have a 521cc engine I am putting together,the problem is it dosnt have an engine I D tag..I am trying to figure out if its a 536 or 537 dont know what year either...here is what I think it is..I think it is a 536 because the cylinders have a bump cast in where the transfer ports are on the outside of cylinders..I think the 537 was more like the 467 with no noticeable transfer port casting showing on the outsideof the cylinder...local dealers are no help..can anyone help me figure this out??I am ready for head gaskets but dont know which ones to get...thanks Rick
 

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ammunta katselija
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showboat45 said:
I have a 521cc engine I am putting together,the problem is it dosnt have an engine I D tag..I am trying to figure out if its a 536 or 537 dont know what year either...here is what I think it is..I think it is a 536 because the cylinders have a bump cast in where the transfer ports are on the outside of cylinders..I think the 537 was more like the 467 with no noticeable transfer port casting showing on the outsideof the cylinder...local dealers are no help..can anyone help me figure this out??I am ready for head gaskets but dont know which ones to get...thanks Rick
[snapback]264495[/snapback]​
It depends on the year. 521cc type 537 is for a formula plus 1986-88 type 536 is for a formula plus 1989-91
 

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mojogunter said:
showboat45 said:
I have a 521cc engine I am putting together,the problem is it dosnt have an engine I D tag..I am trying to figure out if its a 536 or 537 dont know what year either...here is what I think it is..I think it is a 536 because the cylinders have a bump cast in where the transfer ports are on the outside of cylinders..I think the 537 was more like the 467 with no noticeable transfer port casting showing on the outsideof the cylinder...local dealers are no help..can anyone help me figure this out??I am ready for head gaskets but dont know which ones to get...thanks Rick
[snapback]264495[/snapback]​
It depends on the year. 521cc type 537 is for a formula plus 1986-88 type 536 is for a formula plus 1989-91
[snapback]268780[/snapback]​
tip the cyl. upside down, the year should be stamped on the ex. side water jacket.BTW. you hope its the 537, cause doo detuned in 89 so the plus would'nt walk on the new machs.
 

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Discussion Starter · #6 ·
Thanks for the help everyone ,dooho had the answer...87 was stamped by the exhaust port,so now I know what I have..Will let you know how it runs when Im finished putting it together..Its bored .40 over has just been ported, has 40mm flatslides,pipes,and head has been milled and cut....going in a 91 formula mx..
 

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showboat45 said:
Thanks for the help everyone ,dooho had the answer...87 was stamped by the exhaust port,so now I know what I have..Will let you know how it runs when Im finished putting it together..Its bored .40 over has just been ported, has 40mm flatslides,pipes,and head has been milled and cut....going in a 91 formula mx..
[snapback]271758[/snapback]​
sounds nice. Cut the valve too?
The major differences between the pre 1989 521cc motor and the 89 to 92 was the older version put out 85 hp, had a larger crank case(physically) a different rotary valve, pipe and 40mm round slides. The newer ones had 34mm round slides put out 78hp.
 

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HI
I have a 91 formula MX that I put a 521 in a couple of years ago. My Boy didn't add injector oil on the old 462 and that was the end of it.
The 521 that I got came out of a 87 Formula plus but had 34mm carbs on it.
I found it did not perform very well and have just switched in a set of 40mm carbs
and changed the gear ratio from the stock 91 formula mx 26/44 to 26/38. The gears really gave it more legs on the top end for sure. The 40mm carbs just took it to a whole new level. I had it out on the weekend with the stock 40mm carb jetting and the PTO side plug is nice cardboard brown but the mag is heading on the light gray side. I am going to rejet main jet on the mag side up one jet size.

Anyone know what the top rev's are supposed to be on this engine with this setup?
If I hit it and hold it the tac runs up to 8k.
The clutch is still the original from the old 462 Clutch setup with Blue /yellow spring 4.47-4.59 inch don't have a reference for the ramps that I can find. Using the original single stock exhaust.
Appreciate any help
Thanks
Roadrunner1
 

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i have a 1988 Formula Plus would you need any body parts? LMK iam getting rid of it and if u guys need anything just ask Thanks Zach~
 

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ammunta katselija
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Roadrunner1 said:
HI
I have a 91 formula MX that I put a 521 in a couple of years ago. My Boy didn't add injector oil on the old 462 and that was the end of it.
The 521 that I got came out of a 87 Formula plus but had 34mm carbs on it.
I found it did not perform very well and have just switched in a set of 40mm carbs
and changed the gear ratio from the stock 91 formula mx 26/44 to 26/38. The gears really gave it more legs on the top end for sure. The 40mm carbs just took it to a whole new level. I had it out on the weekend with the stock 40mm carb jetting and the PTO side plug is nice cardboard brown but the mag is heading on the light gray side. I am going to rejet main jet on the mag side up one jet size.

Anyone know what the top rev's are supposed to be on this engine with this setup?
If I hit it and hold it the tac runs up to 8k.
The clutch is still the original from the old 462 Clutch setup with Blue /yellow spring 4.47-4.59 inch don't have a reference for the ramps that I can find. Using the original single stock exhaust.
Appreciate any help
Thanks
Roadrunner1
[snapback]272649[/snapback]​
I had an 87 plus I think stock they were around 8100rpm's . I know I had decker pipes, ported, polished, Cut head, larger rotary valve, and 44mm carbs I was turning 8800 rpms. That thing used to fly in its day. Suspension sure sucked though.
 

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Discussion Starter · #11 ·
Wow, now you got me confused..the bottom end was bought on E-bay from a dealer in MN.its pre 89..The only reason I bought it is because I knew where these freshly bored and ported cylinders were, they are 87..the head was from a newer 536 thats why I had it milled and cut..my manual says,85 thru 88 6.5 to 1 comp. 89 up 6.1 to 1 comp ratio..should be around 7.5 to1 if we figured right..the pipes are decker and the clutch is comet 108-c that was already set up for a 521 formula plus..I bought pipes ,cylinders and clutch from same guy...I know this might sound like the frankenstein motor but ,everything was perfect or rebuilt,and cheep!!around $400.00 with new pistons and gasket set..After reading all the replys I hope this thing will all go together!!!and run..If anyone knows something that I might run into trouble with,please let me know....I was asked about cutting the valve,tell me about it,I get the idea I think,give the engine more duration on the intake??do you have any specs.?? thanks,Rick
 

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Discussion Starter · #12 ·
oconnor marine said:
showboat45 said:
Thanks for the help everyone ,dooho had the answer...87 was stamped by the exhaust port,so now I know what I have..Will let you know how it runs when Im finished putting it together..Its bored .40 over has just been ported, has 40mm flatslides,pipes,and head has been milled and cut....going in a 91 formula mx..
[snapback]271758[/snapback]​
sounds nice. Cut the valve too?
The major differences between the pre 1989 521cc motor and the 89 to 92 was the older version put out 85 hp, had a larger crank case(physically) a different rotary valve, pipe and 40mm round slides. The newer ones had 34mm round slides put out 78hp.
[snapback]272359[/snapback]​
thanks,would you have any specs. for cutting the valve,Rick
 
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