1974 XL350 pre-75 advice

[DT_Mania]

I got hold of a '74 XL350. Engine seems good but rest is in parts. Looking to build a pre-75 fighter. Advice please. Especially mods on the engine. Not mayor bank account sapping stuff. Just affordable advice to get the most out of the motor.

Looking to build something like this.

[bazza]

DIET !!  lighten frame and you can save heaps of weight on lighter wheels,forks can be made to work well.Motor unlimited options.I see bike photo has Maico forks and a redline swingarm.

[fatboyracing]

DT,
Be careful if you are going to change wheels you will need a cush drive back wheel as the gearbox on these beasts are very fragile and while definitely brake if you stomp on the gear leaver or dont use the clutch.
I have raced one for years and early on I broke gears but I have since learnt to treat her a bit more gentler.
Engine mods not that cheap but big bore 420 kit and electronic ignition make the most difference. Lighten pull all unnecessary steel parts off such as guard liners etc but dont expect miracles you will only lighten about 5kg this way.

Great fun bike to race have fun

cheers
Fatboy

[sudman]

As per all the other postings, weight is a problem to give you an idea my XL350 sideport race bike is 121kg my C & J framed XL350 is 111kg it's all in the frame & wheels, you must stay with the cush drive rear wheel to keep 3rd & 4th gear intact ( I am currently working on replacements gears to fix that problem) Motor, good port job over bore kit at about 10:1 com (my bikes are just under 400cc for NZ rules) CDI conversion, 36 or 38mm carb works well I run 36's for more mid range punch, lots of good cams about (web's in both bikes) & they like a big fat 44mm pipe header pipe. Lots of fun to ride & can be very fast in the wright hands.
If want any more detailed info just ask.

Tony

On a side note what's the lightest cush drive wheel does anyone run anything other than a XL rear wheel?

[firko]

That bike shown above is a pretty trick unit and if you want to build a similar bike you'll have to factor in $1000 plus for an aftermarket frame like that bikes Redline. It's extremely similar to my old Champion framed XL350. I used Maico forks and triple clamps to gain more rake on my flat track designed frame. I used a Mk8 Bultaco double sided back wheel but the lack of cush drive made it hard on gearboxes, especially that pesky third gear. As Fatboy says using a cush drive rear wheel helps to soften the load on the gearbox.

Everybody has their own way of building the engines but I found that the standard bore and stroke 350 worked better than my 420cc engine using the same compression and camshaft specs. It seemed to rev much more freely whereas the big bore engine had gobs of torque. Each to his own though.

On a side note what's the lightest cush drive wheel does anyone run anything other than a XL rear wheel?

A mate built an XL powered Husky years ago and he found the DT Yamaha rear hub appreciably lighter that the XL heavyweight.
     

[Slakewell]

You can buy chush drive spokets to help, The rear wheel is a pig wieghs somelike 12 KG whilst a YZ mag wheel wieghs 4kg

[sudman]

Any idea who makes then Slakewell?

[DT_Mania]

Thanks for all the advice so far. I'll probably won't go all trick with the bike as in the pic I posted but will go for a similar look. Std frame will have to do for now, go electronic on the ignition and lighten the frame as much as possible.

@ firko - what is your compression and camshaft spec on that free revving 350?

Any advice on the back shocks?
Thinking of going with CR front end. Advice?
Has anybody lightened the flywheel for MX? Or changed to a lighter unit?
Valves?

Cheerio,
Jurie

[Slakewell]

The XL Honda I did make I sold a last year and it had a few good tricks.
310 cc on methanol is enough if your good enough , The 250 crank weighs a good 6kg lighter than the 350 that's a heck of lot forward (not turning)thrust for not much more better power.
The 310cc is fine with the Yamaha rear wheel with a chush front sprocket , I shaved 1.5 kg of my flywheel ( I wouldn't do this if I was running petrol, meth gives a great torque increase) CR 125 tank and Mid 80's husky seat hand made rear brake pedal and set up, cut every bit of non needed bits from frame, 77 XL fork internals give you 7 inches instead of 5. Firko weighed mine at 101 kg at the last Amaro meeting.
I never did but wanted to remove some gears and muck around with the counter balancer.
You can get so much power from the 350 engine that it just forks it up and handles badly give me a good 250 based donk light weight and good handling any day.
Dont know where to buy chush front sprocket I just found the one I had and cant remember how? Maybe 80's XL 500?

[sudman]

The CR250 front ends work well but the spring rate is a little soft but dampering is very good, XL250 flywheel is lighter that the 350 but the lightest is the TL250, my C & J motor is a Long Beach Honda engine so it flywheel has been machine to hell, my sideport has a TL250 flywheel, I run works preformance shocks from the states but most bands work well other than cheap O's, valve sizes are standard on my bikes just s/s as the heads flow well anyway.

If you are talking about sideport motors the XL250 frame is a little smaller & lighter, it doesn't take much to fit the 350 motor in, lots of guys also fit the 350 swing arm into 250 frame for improved handling.

Cheers
Tony
shaved flywheel pic

[DT_Mania]

Cheers sudman. I see the cap reads CDI - is that the electronic ignition mod? What do you use or is it a specifically made CDI mod for the XL350?

[sudman]

It's based around xr200 parts, you use the advancer & cam trigger etc, I have made kits in the passed but don't have any currently.

[Slakewell]

Cheers sudman. I see the cap reads CDI - is that the electronic ignition mod? What do you use or is it a specifically made CDI mod for the XL350?

You can also use CT110 ignitions

[DT_Mania]

Cheers sudman. I see the cap reads CDI - is that the electronic ignition mod? What do you use or is it a specifically made CDI mod for the XL350?

You can also use CT110 ignitions

Tx! I have a friend that has a business building replacement CDI's and converting points to electronic. I'll give him a chance to do the conversion and see how she goes.

Anybody have compression and cam specs? Especially keeping it at 350cc.

[sudman]

Some links for you, I would stay under 11:1, you can also use a XR400 piston but I think you have to bore the pin size bigger, I get my piston & parts from theses guys.

http://www.xlintperformance.com/performanceparts.htm

Cam suppliers
http://www.webcamshafts.com/index_blank.html?pages/vehicle_search.html
These guys list the cam as a 2 valve but it's not they are the correct cam as I have two enter level cams.
http://www.megacyclecams.com/

Cheers

Tony