New head = Premature engine failure... ?

[mk1]

I was all amped up about fitting an ada head ( 37 cc domes ) , an msd enhancer + a new b pipe to my fx1 over the Winter. But a friend has put a damper on my plans by advising me not to tamper with the engine , as a new head would more than likely put a lot more pressure on the engine leading to premature engine
failure. He is basing his fears on the fact that in the past he and his friends have fitted hi performance heads to motorbikes fitted with 2 stroke engines , and had nothing but engine problems further down the road.... Advice please. !

 

[blaster800]

Buy your parts from a known engine builder on this website , Im sure he will be happy to give you great advice on your build to follow along with the parts you purchase . I personally like lots of compression and AM mods . you can stay MILD or go WILD with wild taking more maintenance .

 

[tor*p*do]

if the motor is badly worn, hi comp head may kill it
but it is in need of a rebuild soon anyways
how old is motor since last rebuild?
check compression, look at piston skirts, etc.
it may just need a home and rings and be good to go

 

[RivMan]

Aftermarket Head = Higher Static Compression = More Cylinder Pressure
MSD Enhancer = More Aggressive timing curves = More Cylinder Pressure
Factory B-Pipe = More efficient combustion = More Cylinder Pressure

All of those things will decrease the life of your engine.

I have all three on an engine that's 20 years old without an issue, but you gotta pay to play, my old engine would probably live a longer life without the mods.

-Rob

 

[Lumpy]

I put a Ada head with 33 cc domes, b pipe, and enhancer on a clapped out 701 two winters ago and it's still going strong

 

[XJCrawler]

701's are tough, get an after market head. Just make sure to check your squish

 

[JetManiac]

Completely stock will run the longest without issue, but who wants to ride a long lasting slug?

Remember to rejet and adjust carb for the upgrades and you will be fine. Do a compression check before modding to get an idea of top end condition first. Inspect bores and pistons after pulling the stock head. Take your time to install everything correctly to minimize issues later.

Worst case you blow up your motor completely. Rebuilding isn't that expensive especially just a top end. You can also replace the whole 61x motor with a clean used one for $500ish if needed.

 

[badvinny]

These guys are all correct. And a 37cc head isn't too high compression.

 

[mk1]

701's are tough, get an after market head. Just make sure to check your squish

What is my squish..... ??

 

[mk1]

if the motor is badly worn, hi comp head may kill it
but it is in need of a rebuild soon anyways
how old is motor since last rebuild?
check compression, look at piston skirts, etc.
it may just need a home and rings and be good to go

As far as I know the engine was never rebuilt , but it was left up in a garage for about 8 years before I bought it. It has plenty of power but you always want more.....

 

[keith t]

Squish is the clearence between edge of the top of the piston and the dome, measured by crimping a piece of solder by turning motor over by hand.
Take measurement in line with wrist pin as a false reading can be taken if measured at 90 deg to wrist pin due to piston rocking.

 

[Harbor]

What is my squish..... ??

Here is a thread on it.. You can also YouTube squish measurement and see a little video on it.

http://www.x-h2o.com/index.php?threads/squish-questions.2681/

 

[mk1]

I put a Ada head with 33 cc domes, b pipe, and enhancer on a clapped out 701 two winters ago and it's still going strong

2 years on a clapped engine , that sounds encouraging.....

 

[mk1]

Completely stock will run the longest without issue, but who wants to ride a long lasting slug?

Remember to rejet and adjust carb for the upgrades and you will be fine. Do a compression check before modding to get an idea of top end condition first. Inspect bores and pistons after pulling the stock head. Take your time to install everything correctly to minimize issues later.

Worst case you blow up your motor completely. Rebuilding isn't that expensive especially just a top end. You can also replace the whole 61x motor with a clean used one for $500ish if needed.

what is involved in rejeting a carb , a different needle...?

 

[Lumpy]

Different jets. Look up jetmaniac for your parts. He'll get you everything you need including spot on advice.

 

[Roseand]

I was extremely paranoid about reliability and how a high compression head would affect engine life as well, especially since I was doing a fresh rebuild from the crank up. I bit the bullet and am running an ada girdled head with 35 cc domes, a b pipe, and a cdi with a raised rev limiter. Over 5 gallons of oil in this season with no issues. For safety precautions and since I've got it readily available, I mix 1 gal of 110 oct race gas to 4 gallons of 93 oct premium just to avoid the possibility of detonation when going WOT. Take Jetmaniac's advice and if all checks out, go for it. IMO I'd go for 35 cc domes..It made a night and day difference over stock for me. I was extremely pleased.

 

[mk1]

Completely stock will run the longest without issue, but who wants to ride a long lasting slug?

Remember to rejet and adjust carb for the upgrades and you will be fine. Do a compression check before modding to get an idea of top end condition first. Inspect bores and pistons after pulling the stock head. Take your time to install everything correctly to minimize issues later.

Worst case you blow up your motor completely. Rebuilding isn't that expensive especially just a top end. You can also replace the whole 61x motor with a clean used one for $500ish if needed.

What is considered a healthy reading for a compression test..?

 

[JetManiac]

What is considered a healthy reading for a compression test..?

Most important is that both cylinder read fairly close to each other +-10psi. The compression test will vary based on the guage, methodology of test(plug in/out, throttle held opn or not), and battery strength) but anywhere around 150ish is good. 140ish to 160ish is common.

 

[Harbor]

Don't forget about Elevation effecting the reading as well

 

[JetManiac]

Don't forget about Elevation effecting the reading as well

Good point! Compression will be lower with rise in elevation.