armyofda12mnkeys Posted July 10, 2010 Share Posted July 10, 2010 i found a good deal on a rebuilt 77 xs400 engine that Im debating buying, and while i am working on rebuilding my engine, I want to swap the 77 in so i can ride ... Is there anything i need to look out for? I'm asking as I bought the 77 carbs off this fellow before, and i noticed the carbs are a lillll different (throttle stop screw at the bottom, different float style 'plungers'). but even that seems swappable so I assume the engine is fine too. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted July 10, 2010 Moderator Share Posted July 10, 2010 i found a good deal on a rebuilt 77 xs400 engine that Im debating buying, and while i am working on rebuilding my engine, I want to swap the 77 in so i can ride ... Is there anything i need to look out for? I'm asking as I bought the 77 carbs off this fellow before, and i noticed the carbs are a lillll different (throttle stop screw at the bottom, different float style 'plungers'). but even that seems swappable so I assume the engine is fine too. good to go mate, all sohc's fit! Link to comment Share on other sites More sharing options...
armyofda12mnkeys Posted July 10, 2010 Author Share Posted July 10, 2010 good to go mate, all sohc's fit! sweet!, thanks drewp! Link to comment Share on other sites More sharing options...
armyofda12mnkeys Posted July 11, 2010 Author Share Posted July 11, 2010 sweet!, thanks drewp! Hey drewp. i noticed the engine he's selling has a module for contact lead wire instead of my split wire one (here is a pic of ). also the contact breaker box looks a bit different on the right side... Do you know what year his XS400 is from? he claims 1977 heh maybe he used a 78 xs500 contact breaker lead wire as it looks closer to that, or maybe it is an xs500 engine lol Link to comment Share on other sites More sharing options...
Moderator drewpy Posted July 11, 2010 Moderator Share Posted July 11, 2010 its got the electronic ignition trigger which is usually a later engine (circa 1980) and the engine off a special/heritage type bike due to the rounded barrels. there is a thread in the sticky to convert to electronic ignition if you want to go that route, otherwise sell the trigger mech and revert to contacts! 4G8 engine #? Link to comment Share on other sites More sharing options...
armyofda12mnkeys Posted July 11, 2010 Author Share Posted July 11, 2010 its got the electronic ignition trigger which is usually a later engine (circa 1980) and the engine off a special/heritage type bike due to the rounded barrels. there is a thread in the sticky to convert to electronic ignition if you want to go that route, otherwise sell the trigger mech and revert to contacts! 4G8 engine #? Here is a larger pic: Looks like a 4R4 engine number on there. cool, i can just easily put my contact assembly in there? Maybe I'll work out electric ignition later ... or not, debating how easy it would be to do since im not good with electronics PS i guess since its probably a 80/81 xs400 engine as you said, will work out on a 78 frame? or will some modification of the engine frame need to be performed you think? Link to comment Share on other sites More sharing options...
Moderator drewpy Posted July 12, 2010 Moderator Share Posted July 12, 2010 Here is a larger pic: Looks like a 4R4 engine number on there. cool, i can just easily put my contact assembly in there? Maybe I'll work out electric ignition later ... or not, debating how easy it would be to do since im not good with electronics PS i guess since its probably a 80/81 xs400 engine as you said, will work out on a 78 frame? or will some modification of the engine frame need to be performed you think? As i said all sohc's will fit. if the contacts can be upgraded, then i assume the reverse is true Link to comment Share on other sites More sharing options...
armyofda12mnkeys Posted July 12, 2010 Author Share Posted July 12, 2010 As i said all sohc's will fit. if the contacts can be upgraded, then i assume the reverse is true cool, I shall give it a shot. I'll definately have some questions for you and kmac on setting up the wiring when it comes down to it as it would be my first time doing anything with wiring (probably in a week or 2). A lil intimidating Thanks!, Arian Link to comment Share on other sites More sharing options...
armyofda12mnkeys Posted July 19, 2010 Author Share Posted July 19, 2010 swapped the 80/81 engine in. easy as pie. next comes the electric ignition, got some advice from kmac. looks like just need to connect new wiring to the ground and kill switch. Will update better once done next week or 2. Link to comment Share on other sites More sharing options...
Ebola Monkey Posted July 20, 2010 Share Posted July 20, 2010 4R4 should be an 81. If you want to do the upgrade on it, I would buy new connectors here: . They've got everything you could need, and their crimper isn't half bad either. Link to comment Share on other sites More sharing options...
armyofda12mnkeys Posted July 20, 2010 Author Share Posted July 20, 2010 4R4 should be an 81. If you want to do the upgrade on it, I would buy new connectors here: . They've got everything you could need, and their crimper isn't half bad either. cool nice to know its an 81 On a related sidenote: I was debating checking inside the electronic rotor cover where that connector goes into.... just to make sure its all clean in there (not sure what you'd call it, but its where the contact points on the older model usually go)... and the big hole on the right side has no screw in it... i take out the left side screw and it swivels a bit as if theres a screw still in that big hole... but all i see inside is a perfectly flat area at the end... Should there be a screw in that bigger hole? How do you get the cover off hehe? EDIT: Just wanted to update this in case other peeps are curious... The 'big hole' on the right ride is actually an anti-tamper plug over a screw... Kmac informed me you need to drill it out if you want to reset timing (which usually isn't needed often i hear on these electronic ignition bikes). Also the wires coming out from alternator/stator cover are a bit different on this engine. 1 of the wires has 3 wires going into the end connector when on the 78 it has 4... the extra wire on the 1978 seems to power the headlight? relay assembly ... So I just swapped out my 78 cover and put it on this engine since Im using the 1978 harness (with just 81 electronic stuff spliced into the harness to go along with the engine). Link to comment Share on other sites More sharing options...
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