Hi Guys,

I am wanting to build a new quad, from scratch. I know Laegers will build a frame for this, but they are expensive. Do you think I could make an old R frame work? Which engine would be better suited for a project like this, the CR or the KX? Which one produces more ponies? I've never rode either bike. I'm hoping to find a older bike that I can buy reasonable, '87 or newer. I know some of you have put motorcross bike engines in your quads, so, is there a kit out to turn the kick starter around, or do I have to make do with the way it is? How hard are they to get started? How will I control the vibration? How reliable are these engines? Would a quad with this engine be a complete monster, or would it be comparable to a highly modded 250R?

I know this is going to take a lot of time, patience, and mainly $$$. I plan to do it over the course of a couple of years. I want to do it right, I want to end up with something I can be really proud of.

I'm sorry about so many questions, I am really excited! I've been looking all over for a old bike so I can get this started. They seem pretty rare around here.

Any replies appreciated!

 

the kx has more hp but as for the vibration your going to need to put rubber spacers every where, i dont know of a kit it will take some welding my buddy built one in a r frame the vibration was ungodly but he did not use any rubber spacers check and see if someone makes a counter balancer for the motor i dont think any one does but it would be worth cheaking

 

Use the KX engine. It has a powervalve whereas the CR does not. Either way it probly wont matter because the front end is going to be pointing skywards with either engine.

 

Vibrations, vibrations, and more vibrations. It can be done, but as stated above the non-counterbalanced dirt bike engines will vibrate your quad apart. The vibrations are killer to the rider and machine.

 

How can they get away with this vibration on the bikes? Is it going to be so bad that it's not fun to ride? Do you think I'll need a longer swingarm, and if so, how much longer? and how about that kickstarter? Will it be almost impossible to start when cold?

 

I saw a CR500 in a TRX-R frame on ebay awhile back. It looked pretty good. From what I remember alot of the work was done by CT Racing. Also, if you need a kickstart extension you could probably get one from Houser, they are making them for the CRF and the YZF.

You will also need to do some serious work on making the pipe fit. Vibration is a huge concern, if you can't cut some of it down you will probably not enjoy riding your creation very much.

As for which machine to use the KX or CR, I would try to find out what options you have if you use one over the other. If you can find out some info from CT about the CR than that might be your best bet.

Horsepower wise you are talking about an easy 60hp which is awesome. Most of the pro race quads are more like in the mid 40's. Also, if you can find GT Thunder's website they had a conversion on their website too. They also had some dyno's on the beast

 

I think a better solution is to contact Mac Racing and have them fit a cr 500 head on a fresh 250R bottom. You could get the 250r from service honda for about $2500. You will have everything fit right, including the pipe, you will have a counter balancer. This is the way to go if you want a 500R.

Here is the link is you want to learn more

 

<< How can they get away with this vibration on the bikes? >>



I think it has to do with vibration harmonics. It's not too bad putting a non counterbalanced engine in a trike frame (eg CR500 in ATC250r frame), but putting it in the quad frame isn't as smooth. I agree with trx250Rob; put a 500 head or 400sport head on a 250r bottom end. If you do go with a noncounterbalanced motor, then use big/high dampening mounts.

 

Blackbird - I have also been considering such a conversion.

However, I am planning on doing it with a 400EX frame for a couple reasons - first being that they are easy to obtain and very cheap. the rest of the parts (i.e. plastic, and practically everything else) is cheap and readily available from Honda.

I also would have a much easier time with my conscious chopping up a 400EX frame if necessary than a 250R frame.

I believe vibration can be controlled with frame strengthening and strong, solid mounting. The reason vibration is more of an issue in a quad frame than a bike or 3wheeler frame is because quad frames are much larger and have large expanses of small diameter single tube that is allowed vibrate uncontrollably. If these areas are strengthened, gussetted, and possibly redesigned I believe this can be controlled.

I also plan on using an "anti-vibe" steering stem as well as a set of 1 1/8" Pro Taper style bars - also a set of bar weights if necessary.

I've talked to a couple people about this conversion and one concern I've come up with is a pipe. It seems that the 500 pipe needs some length to it. There are a couple pipes out there that will work, but from what I've heard, they don't have the length to take full advantage of the 500's torque and overall power output.

Another concern is the lack of a lighting coil. This can be cured by throwing a few bills in the direction of eLine for their bolt on stator setup.

The biggest problem I have with some of the conversions like putting a 500 jug on a 250R bottom end is first you are changing the balance of the engine which requires careful mods to the counterbalancer itself (if it can even be modded to balance the new assembly) - and more importantly, the 250R engine was never developed to handle the power output or flow for a 500cc displacement. Then you start running into reliability problems unless you dump a ton of money into the crank, rod, transmission, etc.. Not to mention all the unforseeable problems that crop up with such significant modification.

Personally, I think a much better (and much cheaper) route for the long term is to control the vibration and use the engine that puts out 60+hp with mild modifications. At this point I'm not sure what all it's going to take - however, I will find out and will do what's necessary - even if that involves adding significant amounts metal to the frame...

 

Ok guys,

Thank you for all of the ideas.

I have a line on a '87 KX 500. Haven't saw it yet, but talked to the owner, he says its in great shape, stored most of its life. I have a guy wanting to buy the rolling chassis less motor, and says if its good he will give me $300 for it.

To your knowledge, are there any problems with that year engine? Would it have the 60 horses?

What should I expect to pay for it?

BTW 1986atc250r, I agree with you. I am a little skeptical about using a bottom end designed for 33 horses or so with a displacement twice the size. I think I'll try to deal with the vibration, even if it does mean I'll gain a little weight.