talk to billy at wrh racing. he is the predator expert, his son races 3 of them.

Mark

 

snowdust

come on over aug.6 to warren il. storm mx the race is during the fair. its a good time

 

I'll let my sister know about the track in Warren. I'm not too sure how far that is from us, but I will check it out. Thanks!

Fastest....How much do you want for the head? I'm assuming it's from WRH?

Thanks!

 

I sent you a pm look at the flashing icon at the top left of the page. I sent you dir. to use PM system. No the head is a hetrick mod and its a cast head not one of billys. His are a very nice billett head I had a gold one but traded it off. Sent you a Pm. If you dont want mine I'd still get one from billy or rich. The stock compression is really weak (100-110) psi and the bikes run much better with more compression (140-160). Takes me about 10 mins to change the head, very easy mod and I can usually run 1 size larger mainjet cause it will burn fuel better/more power. I have 2 heads we use one for trails and one higher comp. when dragracing.

 

Ok guys. I did some testing tonight. Forgive my wording as I am helping my nephew... I'm new to the 4-wheelers. It doesn't seem to have the low end I would expect. I found out that with the smaller tires I have... changing to a 31 or 32 gear (can't remember) just got me back to stock gearing. For clutching...6G rollers...yellow spring...weights are drilled out...new belt. It seems to keep pulling RPM's as it winds out. I'm used to tuning a snowmobile where you have a tach. This is a little more difficult. From everything I have read on the forums I think most are running a red spring and between 5-6G rollers. It also seems like going to a 27-28 tooth sprocket seems to help. I will be getting a 20MM carb next weekend, and a UNI filter. Hopefully that will make a big difference. I don't expect that to solve my low end problem though. What do you guys think? I am thinking of trying the 5G rollers. I would also like to know if I should be running a red spring instead of a yellow. I do not know the rates on them. Thanks for any help!!

 

You are about right I'd say as far as roller weight. The bikes with pipes dont have very much low end power unless you use an aftermarket rear clutch(lighter) and you need to get the thing more than the 100 psi compression it has stock. You will want it to have about 140-160psi for pump gas. Your new 20 mm carb will help it more than you think on topend and a little down low. Good porting will about double the power you have now when he's ready.

 

If you were trying to keep it cheap.... Do you think it is worth it to just take .030 off the stock head... or is there not much of a gain unless you get the chamber re-shaped?

 

The stoch heads are messed up in squish shape/design they are a piece. WRH said to take it off the cylinder to get it to 77mm gasket to gasket I'd listen to him. You need to be able to measure your squish clearance if modifying the head and no just milling the head .030 wont fix the stock heads problems. Halfway ok 1982 scooter head design copied and screwed up by chinese reverse engineering. WRH Billys got some funny Alabamean terms for this bad engineering I just cant remember them.

 

LOL Thanks. From everything I have read I think I would have just cut it .030 for now. Sounds like my nephew will need to save up some money and do it right. When we get that far I will call Billy for suggestions. Thanks again for the responses!!

 

When you are dialing in the clutching, are you using a tach somehow? I'm used to tuning the clutch to run at the RPM the machine makes it's power. I don't see anyone talking about a tach on here, so I am wondering how everyone is getting these things dialed in.