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    NT400 To NT700

    Forgive me if this has been covered before, but I've had a look around and can't find the answer to the scenario I'm considering...

    Short story long, I accidentlyed a NT400. These bikes have popped up on my radar over the years as cool little bike ripe for modification so I've ended up with one. From my simple understanding in short you dump the NT400 engine but keep the gearbox, flywheel, and CDI and replace it with a NT650 lump with those bits swapped in and then add a big bore kit to get to 700cc. My problem is sourcing the NT650 engine.

    I'm in the UK and from what I can tell the NT400 and NT650 were not official models. The NT650V with the shaft drive was. The problem there is that I don't want shaft drive and there is a difference in the cases. So what can I do to get to 700cc?

    My thoughts are import a NT650 engine, the problem here is cost, not so much the engine but the shipping and import duty starts to make it a little silly. So the other option is to swap out the internals of a NT650V engine into the NT400 cases. I know that they share lots of parts but I know there are some that would need modification the problem is I dont have a definitive list of what is possible.

    So what is the collectives thoughts? Am I barking up the wrong path? What would you do to make a 400 a 7?

    #2
    Buy a vfr750

    Comment


      #3
      They are some discussion about upgrade 400 engines to 650 and after that only the work from 650 to 700 required
      AT 750 engine or hawk bros 650 engine are not so rare un UK my brother livescthere and he had 2 bros 650 that has ben stolen, so enough spare supply....

      Comment


        #4
        Originally Posted by squirrel_hunter View Post
        Forgive me if this has been covered before, but I've had a look around and can't find the answer to the scenario I'm considering...

        Short story long, I accidentlyed a NT400. These bikes have popped up on my radar over the years as cool little bike ripe for modification so I've ended up with one. From my simple understanding in short you dump the NT400 engine but keep the gearbox, flywheel, and CDI and replace it with a NT650 lump with those bits swapped in and then add a big bore kit to get to 700cc. My problem is sourcing the NT650 engine.

        I'm in the UK and from what I can tell the NT400 and NT650 were not official models. The NT650V with the shaft drive was. The problem there is that I don't want shaft drive and there is a difference in the cases. So what can I do to get to 700cc?

        My thoughts are import a NT650 engine, the problem here is cost, not so much the engine but the shipping and import duty starts to make it a little silly. So the other option is to swap out the internals of a NT650V engine into the NT400 cases. I know that they share lots of parts but I know there are some that would need modification the problem is I dont have a definitive list of what is possible.

        So what is the collectives thoughts? Am I barking up the wrong path? What would you do to make a 400 a 7?
        It is too much work, keep the 400 a 400, unless you put a complete motor in it (650?) plus there is the insurance to think about, I am with jet black, buy a vfr, modified they look great

        Comment


          #5
          I suspect you could check ebay and buy the heads, cylinders. 700 pistons are going to be a direct buy from Wiseco in your neck of the woods anyways. last I checked I don't think JD will ship parts overseas so much but you can try giving him a call and see. He might make an exception for a lightened piston kit. After that it's a matter of jetting the carbs (unless the carbs are different overall as well). Seems the cheaper route to go overall considering it would cost much less to ship the parts compared to the weight of a whole motor.
          88 Blue Hawk GT - Under construction but rideable (guest approved)
          89 BlackHawk 2.0 - On the lift and being assembled
          90 Hawk GT (color as to yet be determined) - Still on the shelf in crates

          Comment


            #6
            Originally Posted by Luis View Post
            They are some discussion about upgrade 400 engines to 650 and after that only the work from 650 to 700 required
            AT 750 engine or hawk bros 650 engine are not so rare un UK my brother livescthere and he had 2 bros 650 that has ben stolen, so enough spare supply....
            Yeah the NT650 does exist over here, but there I can't find anything for sale at the moment. Sorry to hear about your brothers bikes being stolen its disgusting that these things happen. As for the AT750 I was reading on here that its a bit underwhelming so thats why I want to go for the 650/700.

            Originally Posted by yorkshire View Post

            It is too much work, keep the 400 a 400, unless you put a complete motor in it (650?) plus there is the insurance to think about, I am with jet black, buy a vfr, modified they look great
            I'm not afraid of putting the work in, this wouldn't be my first rodeo and I've got nothing against the VFR, but I don't have one of them lurking in my garage...

            Comment


              #7
              Originally Posted by rpcraft View Post
              I suspect you could check ebay and buy the heads, cylinders. 700 pistons are going to be a direct buy from Wiseco in your neck of the woods anyways. last I checked I don't think JD will ship parts overseas so much but you can try giving him a call and see. He might make an exception for a lightened piston kit. After that it's a matter of jetting the carbs (unless the carbs are different overall as well). Seems the cheaper route to go overall considering it would cost much less to ship the parts compared to the weight of a whole motor.
              Yeah I've been looking on eBay and I can get a complete NT650V engine in this country, but just need to be sure that I can essentially recase it and what if any work other than sticking it all back together is needed?

              As for carbs I'm thinking that a set of FCR's would be in order...

              And forgive me, I'm new here, but who is JD and what might he do?

              Comment


                #8
                JD is a US shop that sells stock and upgrade parts.
                88 Blue Hawk GT - Under construction but rideable (guest approved)
                89 BlackHawk 2.0 - On the lift and being assembled
                90 Hawk GT (color as to yet be determined) - Still on the shelf in crates

                Comment


                  #9
                  Originally Posted by squirrel_hunter View Post

                  Yeah I've been looking on eBay and I can get a complete NT650V engine in this country, but just need to be sure that I can essentially recase it and what if any work other than sticking it all back together is needed?

                  As for carbs I'm thinking that a set of FCR's would be in order...

                  And forgive me, I'm new here, but who is JD and what might he do?
                  Hi, Is the nt650v the shaft drive engine?, I have put 600 barrels on a 400 but I believe they are the biggest barrels that fit into 400 cases without opening up the case throats, I used external oil feed to the cylinder head, I believe the 650 shaft drive maybe all internal oil feed? the 600 clutch is slightly different, it has more plates but fits, the actuation lever area needs work.

                  Comment


                    #10
                    Originally Posted by rpcraft View Post
                    JD is a US shop that sells stock and upgrade parts.
                    I think I've found him, https://www.hordpower.com/ some nice bits there...

                    Comment


                      #11
                      Originally Posted by yorkshire View Post

                      Hi, Is the nt650v the shaft drive engine?, I have put 600 barrels on a 400 but I believe they are the biggest barrels that fit into 400 cases without opening up the case throats, I used external oil feed to the cylinder head, I believe the 650 shaft drive maybe all internal oil feed? the 600 clutch is slightly different, it has more plates but fits, the actuation lever area needs work.
                      Yeah the NT650V is the shaft drive. Essentially the question is can I take everything out of a shaft drive engine case apart from the gearbox and shaft drive output and stick it in NT400 cases?

                      Had a look and the NT600 appears even rarer over here. But thats an interesting point regarding external and internal oil feeds. Will have to check which one my cases use, but then that gives the pre-emptive question of is it possible to convert between the feed types if required?

                      Comment


                        #12
                        I don't think you need to take out everything really, just look the heads, cylinders and pistons over and swap them. Test fit everything and measure where possible of course.
                        88 Blue Hawk GT - Under construction but rideable (guest approved)
                        89 BlackHawk 2.0 - On the lift and being assembled
                        90 Hawk GT (color as to yet be determined) - Still on the shelf in crates

                        Comment


                          #13
                          Originally Posted by squirrel_hunter View Post
                          As for the AT750 I was reading on here that its a bit underwhelming so thats why I want to go for the 650/700.
                          I wonder why anyone would say that about the XRV750 engine in the Bros/Hawk frame? I'm running one of these engines in at the moment and am very pleased with performance. The only engine modifications that I've done apart from intake and exhaust is a mild gas flow and a JE forged piston kit intended for the Hawk/Bros, which increases the cc to 760 and ups the compression. The resulting engine is very happy to pull 17/40 gearing.

                          Comment


                            #14
                            I could have been wrong about the AT750 engine, forgive me, might have been more around using parts across the models and the work against reward. But either way its a moot point at the engine seems to be rarer and far costlier here then even getting a NT650 shipped in from the colonies.

                            Comment


                              #15
                              Originally Posted by yorkshire View Post

                              I used external oil feed to the cylinder head, I believe the 650 shaft drive maybe all internal oil feed?
                              So I've checked and the NT400 engine I have is external oil feed, the NT650 appears to be internal oil feed. It was about this time I found the following thread https://www.hawkgtforum.com/forum/ho...f-build-thread which I can't believe I missed. The short summary is NT400 to NT600 looks easy as both use an external oil feed. NT400 to NT650 is complicated as the 650 uses an internal oil feed. Now while I dont mind doing some work but this is well out of my level of incompetence. And as the NT600 is just as plentiful as the NT650 I've discounted that idea as a way of getting from 6 to 7.

                              However fear not I have a plan, a cunning and subtle one, as cunning as a fox who's just been appointed Professor of Cunning at Oxford University. A build thread will be appearing in the distant future...

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