550 Seca Cam/Head Swap

Hey everyone,
I haven't been on here in a while, and I'm sure someone has already gone down this road before but I can't seem to find it. I'm looking at doing a top end refurb (valves, seals, guides, etc.) on my 550 Maxim sometime in the future and recently stumbled upon a 550 Seca that's destined for the junkyard shortly. The Seca is very rough and incomplete but the engine seems like it should be fine with some cleaning. I'm thinking of getting it and refurbishing the Seca head and then putting it onto my Maxim once it's done, rather than putting my Maxim offline while the work is done. Is the head a direct swap between these bikes aside from the difference in carb jetting?

 

The cams are different (although Maxim and Seca cams will physically swap) so the heads will swap just fine. If the Seca cams are used, then you should change the jetting (and main jet needle) to match the Seca configuration.

 

Are the OEM bs28 carbs still on the bike. What year do you have. I would use them. You will experience idle problems. Chacal is has all you need for the jetting if you don't have the correct jets. You will need a 170 jet for the air orifice on top and the 4GZ11(SECA) needle jets.

 

the other differences in maxim and seca is rear tire on seca is bigger diameter thats what gives the seca a few more mph in the top end.
seca is also about 1/2 sec faster in the 1/4 mile.

i guess what you have to ask your self is it worth the time and expense for 1/2 to 1 second quicker.
you would not get the additional top end because thats determined by the rear tire at max rpm.

if you can get the whole bike cheap enough you could keep the motor and sell whats left of it off setting the costs
or swap out a few parts onto the maxim , Dual chrome horn set up on front forks would look good

 

It's an 81 Maxim, with the original mikunis. Not really interested in going faster, just want to fix the oil burning issue with my valve guides right now and this parts bike is the right price. Unfortunately there aren't many other salvageable parts on the bike...

 

are you sure its the valve guides and not the guide seals ?
the seals are an easier fix that can be done with head in place

 

if you need to rejet to swap seca head in it ain't cheap for the slide needles air jets are not to costly.
it would just be easier for you to remove head fix it and reinstall if you have to change the guides.
and save some cash in the long run
if your getting the seca carbs with the head once you put them on you will not change back.
cl on west coast seca that is being sold for parts may have a carb set for you

http://seattle.craigslist.org/tac/mpo/5414739406.html

real shame he's parting it out

 

Sorry, I assume it's just the valve guide seals, but figured it would involve pulling the head and I would lap the valves while I was at it. I thought it would be easier to have a spare head to do the work on and then just swap it over once it's done but it sounds like it might end up being more hassle than it's worth. Thanks for the help!

 

If you wanted to have a spare head you would be better served rebuilding a head that is off the bike then installing it.
instead of swapping a head , rebuilding it and putting it back on. the head gasket cost$$ (if done right you would replace it twice the way you wanted to do it ) and you would have to use 2. 1 each time you swapped head.
if you want guidance in replacing seals or testing, start a new thread on that subject, and you could put a link in it to this thread.
that would make it easier for others to search for the subject"oil burning rings, valve guides and seals testing and replacement"

just asking but how have you determined it is the guides that leak oil?

 

I did a compression test a while back, it's not the rings.

My plan was to get the seca head, rebuild it while still having my bike online, and then put it on my maxim after it was rebuilt, only swapping once.

 

when you swap it you could go with the maxim cams or upgrade the carbs