87 gsx400x motor/89 gsxr250 frame

[durpleds]

Hi all. I am in the process of putting a air/oil cooled gsx400x motor into my gsxr250 frame.

I am at a standstill regarding engine clearance. I have read that I need to grind the head bolts a few mm to slip in.

Is this correct and does anybody have or know of further info that might be helpful.

If you have experience in this, your knowledge will be much appreciated.

Thank you in advance for any help.

 

[GregT]

Welcome to the forum. Pre 89 race bike ? Interesting build.
The GSX400X motor -Impulse ? - has no mounts on the head AFAIK so i have no idea what head bolts are referred to.
All you can do is offer it up to the frame and see where it might need trimming.

Built a couple of Impulse motors back in the early days of F3 here. Quite rugged.

 

[durpleds]

Hi GregT

Thank you for your welcome and help.

I'm building it up to be my roadbike, I have 2 complete bikes to do it from. The gsx400x/impulse is De registered, so I figured the extra 14hp it provides will be great in gsxr250. I can see the bolts that another forum mentions. However it wasn't a very detailed forum. Someone mentioned GSResources, so glad I am a member now because what I have looked through so far on here is pretty cool. I am trying to avoid attacking my motor with a grinder incase the other forum is wrong. Don't want to de-value the motor if it won't work.

Some will say "buy a bigger bike". I am limited to power to weight ratio on my license here in NZ. So I am doing a bit of a cheeky.

Awesome that you raced F3. That is a goal of mine in the next year. Do you have any performance modifications that don't require stripping the motor down that you can recommend?

 

[GregT]

Trying to make a LAMS special ? That is cheeky.
Back in the day, just a louder can on the stock Impulse pipe worked quite well. You've got the twin two barrel carbs of course which aren't easy to tune for any major changes. I can attest that a well prepped Impulse motor in the hands of two very hard riders will last 2 1/2 seasons before breaking a rod...but that was using an aftermarket ignition box and around 16000 RPM....
There are no easy carb alternatives either, sorry.

 

[durpleds]

Lol yes officer, I gained 14hp with my afm can lol.

That's impressive, really cool to hear that.

Thank you for all your help Greg.

 

[durpleds]

Well the motor is in, both rear top and bottom mounts are fitted. I have the front cradle mount to modify. I have connected it all, and it's winding over. I haven't done fuel, cooling or exhaust yet.

Rather proud of myself, first heart transplant that I have performed. My be a simple one in others eyes, but for me it's a biggy. I will add a photo in the monthly GS forum when the bike is complete. Got a few trick plans up my sleeve.