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Old 05-17-2006, 09:57 PM   #16
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How much pinch should I feel on this engine. I have this engine with only 10 tanks ran through it (some would say its not even broke in yet) and now with engine at room temp and glow plug out, I can feel some pinch but can pretty easily turn it over. I tried the same test with my 12tz and can't get it past TDC. These tests are done in the cars and turning the flywheel from bottom with my finger. If the 21vz-r is too loose I can't understand why, because we always preheat the head to 220 degrees F. bafoe starting and during breakin on the breakin bench have wrapped the head with aluminum tape and maintained at least 200 F. with a heat gun. Then left the tape on when we ran it around in the car with at least 170 F. So does a 21 have less pinch then a 12? Or is my p/s wore out already? We just touch it to the starter box and its running and it has very good power in the car.
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Old 05-17-2006, 11:47 PM   #17
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I have a a VZ-R that I just replaced the piston/sleeve in (never started), and with the plug out, it has just a light pinch at TDC just as you describe. My other VZ-R has several gallons through it, and it has seen 280 F a few times..... still runs excellent. I think its just starting to break in, you have nothing to worry about.
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Old 05-21-2006, 09:00 PM   #18
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Quote:
Originally Posted by graphiteman
I have a a VZ-R that I just replaced the piston/sleeve in (never started), and with the plug out, it has just a light pinch at TDC just as you describe. My other VZ-R has several gallons through it, and it has seen 280 F a few times..... still runs excellent. I think its just starting to break in, you have nothing to worry about.
Do these motors have con rod problems? we had two 1/8 onroad racers loose rods, both engines were new, both on there 15 to 20 tanks, the rods broke above the crank pin. I have never seen a rod do this. the one motor is junk, rod went out the bottom and toasted the sleeve also.
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Old 05-21-2006, 10:43 PM   #19
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Default O.S. VZ-R

I have not had any problems with mine thankfully. I wonder if there was a bad batch of rods from OS? I don't run any more than 30%, and lately the 25% with the INS Box. Did you take time to break it in before running it hard?
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Old 05-21-2006, 10:50 PM   #20
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the conrod in my 7 tank old vzr let go yesterday
and the thing is it wnet at idle and stripped the gears in my new mrx4

i was driving it slow at rich around the track running in the engine then i came in to pit lane to refuel as i took off the conrod let go just above the bushing

all the expert racers at the track said it seamed to be a manufacturing fault and should send it back under warranty. the lhs said nope its normal for engines to blow rods (blah) and he tried to sell me another one.

im gonna email os engines direct and tell them that there local distributor here is being an ass about the whole thing. hopefully they can help me out seeing that the engine is new.
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Old 05-23-2006, 11:24 AM   #21
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I was one of the two 1/8th scale Rose City Scale Racing members who's con-rod let go after 20 or so tanks. I am hopeful that Tower hobbies will make it right. I'll let everyone know.
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Old 05-30-2006, 07:48 AM   #22
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I bought mine brand new took it apart and measured everything, crank timing, port timings, crank pin. conrod. I thought there was to much clearance in the rod and crank pin when it was brand new. After break in and 1 race day crank pin is worn .0005 out of round and conrod appr. the same giving it another .001" play in the crank pin and rod.
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Old 05-30-2006, 09:43 AM   #23
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I dissasembled mine when new just to clean it. I do remember it being very easy to slip the rod onto the crank pin. Wish I would have checked the measurements before I sent it back. Thanks for the info.
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Old 06-02-2006, 09:35 AM   #24
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i had my local hobby shop send the engine back to the distributor as he also believes this is a manufacturing fault with the rod.

the distributor just said see page 17 of the manual as the engine is not covered under warranty! this sux

i sent a nasty email to os in japan hoping they can do something. i also mentioned that iw ould not be using OS engines any more if they cant help me.

ill see how this goes
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Old 06-02-2006, 10:34 AM   #25
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I guess I'm fortunate to have purchsed my vz-r from tower. They have shipped me a new engine due to the total destruction of the engine. Not taking chances I ordered a new rod and connecting pin for after break-in.
It has been suggested thet I sell this motor and buy an italian plant but I think I'm going to give it another chance.

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Old 06-04-2006, 07:40 PM   #26
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I lost my Conrod this weekend at the MWS in Toledo, and another guy lost his. I had less than a gallon on this engine. Damaged the sleeve but piston is ok. If I can get the sleeve out I think it can be salvaged with a new Rod. Looks like a new rod with every gallon.
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Old 06-05-2006, 08:44 PM   #27
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Makes me wonder if the con-rod is not up to the task. I bought the motor after seeing one run and win the roar regionals in Seatlle. That motor is still running fast this season. I'm hoping the con-rod I bought to throw in after break-in may be from a different batch and not suffer the same fate as the last one. Anyone have thoughts on this?
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Old 06-07-2006, 07:51 AM   #28
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i opened my engine up today and the piston/liner are perfect
im gonna replace the conrod then sell the engine...

going to buy a trusty max power MF
heaps more money but i hear these are awesome engines to stick with
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Old 06-12-2006, 01:16 PM   #29
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I'm going to pick-up an MRX4R soon and I would like to get one of these motors. I see reviews are mixed on this motor but this will be my first 1/8 on road, will this motor be good for me? I'm not going to race any Worlds or National events I'm just going to race at my local track thats all.
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Old 06-12-2006, 02:15 PM   #30
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The performance and price are great. I worry about the conrod situation, seems to be more of these letting go in this engine than I have heard of before.
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