Author Topic: engine mod question, 85FL350R  (Read 3468 times)

lucky luciano

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engine mod question, 85FL350R
« on: September 07, 2009, 03:16:51 PM »
so i just recently got an 85 FL350R about a week ago, maybe.  runs great, but i wanna do mods to it for trail riding.  ive been reading on a few forums about some bolt on mods. mine already has works shocks on the rear so i want to do something to the engine and eventually get a bolt on a-arm style suspension for the front.
   my questions:
1.  if i get an oversized carb for it, what other mods would i have to do to "compliment/accomodate" that? (liquid cooled head, more airflow into the airbox, pipe, ...)

2.  can i run a trx250r 34mm or an older cr250 carb(not the 38mm, but the 36mm i think it is)? if not what should i run?

3.  i heard somewhere that the comet 94c clutch engages at a lower rpm, is this true? i  if so does the comet 102c also engage at a lower rpm?

LiveWire

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Re: engine mod question, 85FL350R
« Reply #1 on: September 08, 2009, 05:36:03 PM »
The first thing is to make sure everything is in good working order. You do not want your top end to fail after installing a new carb. I personally would not run a 350 I bought used until I took the top end apart to inspect. If you do end up getting the top end rebuilt, porting is the biggest bang for the buck power mod. You can run a 35 PWK on an otherwise stock engine. A 39 PWK will run fine, but you will not see any additional power without porting and/or pipe. The water cooled head will reduce the heat output from a modified engine regardless of how you are making additional power. A 34PJ should work if you can find one that is not worn out. I used a PJ before going to the 39PWK and greatly prefer the PWK. None of the larger carbs fit the stock intake boot. The 94C engages lower than the 102C, not lower than stock. Both engage higher than stock. I suggest the 94C if your primary concern is replacing a worn stock clutch and the 102C if your primary goal is performance.

lucky luciano

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Re: engine mod question, 85FL350R
« Reply #2 on: September 08, 2009, 08:13:38 PM »
thank you for the advise first and foremost.  my plan is to run the current top end for 1 or two more rides, and then rebuilding the top end at least.  by the time i do the rebiuld, i will hopefully have some cash set aside for a liquid cooled head, an oversized carb(most likely the 39 PWK that you mentioned) and a dg exhaust.  i plan on also doing a port job while the engine is apart. is there any thing else that you would suggest doin while im at it?
  i do have a couple more questions for you, livewire, at least for now haha.

  is there any way that i could get shorter a-arms with that bolt-on long travel front suspension kit thats on your site? i want to widen the front end to about 56" as opposed to the near 60"(i think) that the long travel kit normally is.  i also have heard that the yfz450 a-arms and shocks will fit onto the bolt on bracket for the long travel kit. is this truth or myth?
  also what could i do to get more low end, not that i really need it but i would like to be aware of all the potential performance the machine is capable of.

                                        again, thank you for the knowledge and advise livewire, lookin foward to see your response

LiveWire

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Re: engine mod question, 85FL350R
« Reply #3 on: September 09, 2009, 04:34:09 AM »
Stock Pilot arms will fit if the pivot bushings are replaced. Shorter shocks would need to be used. Stock Pilot or Works for a Pilot would work, but since you would still have the anti bump steer, it could handle more travel. I have never looked at YFZ450 arms. It would surprise me if they bolted up. With stock wheels all the way around, the kit makes the machine 59 in the front and 58 in back. Narrowing it to 56 in the front won't fit you through anything you could not before. If it is not about fitting, but clearance to trees at speed, I would rather have the agility the kit gives with less clearance than more clearance and less predictable steering.

To make power at the low end, you would use a 35 carb instead of the 39. The cylinder could be just cleaned up when ported without raising the exhaust port roof and widening the exhaust port. Some refer to the Power Pros pipe as a torque pipe. It was intended to be a rev pipe, but just does not make as good of power as the DG. So I really don't have a pipe suggestion other than stock. The top of the cylinder can be shaved to decrease squish clearance. The Aftershock head already has a better 14 degree squish angle, but cannot be lowered any more than it already it.

My advice though is to just tune everything together for what is readily available. You'll get more power under the curve tuning to higher RPM than trying to shift the curve down. Tune the clutch to the power and it doesn't really matter where it is made. If concerned about engagement RPM and the ability to cruise trails, I use a Heel Clicker kit in my 102C clutch. Engagement RPM is far lower than the standard 102C calibration and if cruising around slow, the RPMs are lower. However, the machine will still pull out of the hole harder.

lucky luciano

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Re: engine mod question, 85FL350R
« Reply #4 on: September 09, 2009, 01:43:38 PM »
  again thanks for the info.  for the most part, the trails i ride are fairley wide, but some trails i ride are really tight, to the point where i have to slow down and pick certain paths around/over things.  i know the a-arm front suspension will drastically improve the handling, but i feel like i would have harder of a time in those real tight trails with a 59 inch wide front end.  so i figure ill just make a comprimise with the pilot a arms, give up a little handling and stabilty for trail accessability(i guess you cou call it).  eventually all the trails around here will be wide enough for the longer a-arms, but until then i still gotta ride, haha.
  im not sure about the pipe, but the silencer is stock off of a trx 250r, ill have to take a closer look at it.

lucky luciano

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Re: engine mod question, 85FL350R
« Reply #5 on: September 09, 2009, 01:48:48 PM »
  thanks for the advise on the clutch, im deffinately gunna take it.  once i get my cash flow in order ill be getting in touch with you for parts, livewire