FI for XR650L 2008?

How do you deal with the heat that high power output always seems to come with? My mostly stock XR600 has heat issues with extended wide open runs. I start to get pinging on pump premium even though I'm only running the stock 9:1 compression. I've had to go to a 165 main jet to suppress it on a recent long distance high speed ride.

So do you deal with it by only doing short durations of high power, or have you done other mods to help the engine dump excess heat?

Those are some cool looking toys. It looks like a lot of fun. If you have the time drop us a note from time to time. I think that everyone here will be waiting.

We have not really had any heat problems. For one thing we made a piston squirter and our own oil pump. Secondly we machined our own billet piston with plenty of thickness. No coating, coating is bad. And finally maybe the higher speeds and less single track (which is never) maybe help with the cooler temps. Our bikes are reving to 8500 most of the day trying to keep up with the vtwin gator we have. We actually are cutting the fins off the motor to fit our frame. But I think its the squirter.

XRLTIM thanks for the words on my boss he is a great guy and a living legend. He did however celebrate the champenge blast in 1967. We still have the bottle. Probably one of the most expensive empty bottles of champenge ever.

damn stepho, i wish i worked with you guys!!!!:thumbsup:

got any use for a MDT Toyota tech (hybrid certified) with 13 yrs ????? LOL


Im intrigued how youve got a straight downdraft inlet tract without losing the base support for the valve spring.

No problems with pinking on my engine, running std ignition so far, 675cc, 11:1 (small dome head) and 97RON unleaded. Engine runs hot but I do use an oil cooler. Surrounding beam chassis gets very hot after a race track session tho!

Stepho, Interesting that youve not had limited success with the D-shaped exh port. Most of the tuners in the UK still use them incl the FWD Manx Nortons which are making very good power (65-70 rear wheel HP from an aircooled push rod 500cc single!). Maybe its not so crucial on the twin ports of the XRL head?

I love this site!You people are awesome!I'm a horsepower junkie,Stepho,you got to share some more of your secrets with us fellow thumper additics.I remember watching a program about the alligator several years back,for some reason it never cought on around here,or were they ever sold to the public?We are all ears Stepho.

WOW. Just seeing those pics gives me a funny feeling in the seat of my pants!!! That setup is wicked!!! How/where/from who can I get a setup like that??? Stehpo, you've got a laundry list of questions that have already been asked, but if I could, one more? I noticed in one post just recently you said

No coating, coating is bad.
, are you reffering to a ceramic coating? If so, why does that = bad? I have always been lead to believe ceramic coatings are good, by dissapating heat, no? I would really appreciate your knowledge as I'm in the process of rebuilding my XR600R and had seriously considered a ceramic coated piston, should I not? Please share, it is obvious you are a world of knowledge.

yes we did sell some customer gators 26 are out the door with about 10 more to go. One of the hardest things to do is to put a freeze on design and actually make a bike and repeat that with the following bikes. We are constantly riding things, testing things, breaking things(well not so much), and making things better so a lot of trial and error has happened when you double the output of this motor. When we were first doing the FI we were having a hard time keeping the ceramic coating from galling the sides of the cyl. So we changed a little design on our piston and it worked out for us. No coating. On the old 600xr We used a wiseco piston and that worked well so thumbs up on that. As far as the port design for the exhaust, we just didnt get the numbers we wanted out of them. Tried larger valves on exhaust didnt help either. So the exhaust port is definatly not as inportant as the intake. Take about .100 off the exhaust port valve guide and it will give you more result. Have not noticed any problems from doing so. But focus more on intake.

Yes, Most of the work on my head is on the intake side, nothing major tho. I normally take a bit off the valve guides anyway as they seem to have plenty of support length for the valves. My 675 is making 55 RWHP so is pretty healthy to say its unning a std 650 CDI. My next mod is to change the CDI to a programmable one. I have this on order ready for some more dyno work. Im hoping to get 60 HP with ignition mods. I'll take a rest then!

I guess future mods will be a coated ally cylinder for a bit less friction and weight and dual intake based on XL600. Is the fuel injection mod something that youll be offering to cutsomers? I guess the costs involved are pretty crazy. I expect I'll stick with my XL600 head with dual RGV250 carbs for starters! :oD

hey CC the system we use is made exclusively for the gator but like I said earlier we had better luck power wise with the twin 39 fcr 675 version rather than our 706 xrl with FI. But the street ablity is better with FI.

Have you guys found the fatal, unfixable power limit with the 600-based engine design yet?

I've been playing around with a MegaSquirt and have several turbos in my collection. One of them is a Garrett GT15 and although small, will support 120+hp. :thumbsup:

And just for the record, Ford built GT40s in the '60s; the new ones are simply GTs. The new short model name seems to be confusing some people about the original's model name.

Troy Lee just came to the shop today. Rode the gator said it felt like riding a formula car. That was awsome. Nice guy. Working on some project with him in the future but cant say anything sorry.

PS. Just bought 04 crf forks for my smxrl and a emig racing stem. Its all coming together soon. Its going to be a busy winter, thats for sure.

Stepho, excuse my ignorance, but what actually is a Gator? My excuse for not knowing is being in the UK!!

A-Ha - I just checked out your garage!

go to and check us out, cc.

Looks like you get to work with some pretty sweet stuff.:thumbsup:

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now