TRX 90 Big Bore Install - NEED HELP!

[mrman5050]

I'm trying to install a 114cc big bore cylinder kit on my son's 2005 TRX90. I am re-using the stock cylinder head assembly.

My issue/question is with the air suction valve tube that mounts to the stock cylinder. The big bore cylinder does not have a port to accept this tube which is fine as it is easy enough to eliminate. HOWEVER, the stock cylinder head has a small port that runs from the exhaust port, through the cylinder head and into the cylinder (eventually exiting out the now-eliminated tube).

Since the big bore cylinder does not accomodate this tube, the top of the cylinder was not designed to specifically mate up with the bottom of the cylinder head to effectively block off the "exhaust" hole in the bottom of the head.

From what I can see, if I try to use this cylinder/head combination I will have two problems, 1) hot exhaust gases will be dumping directly on to the cylinder (bad) 2) I will have one heck of an exhaust leak (also bad).

My thought was to simply JB weld the hole in the cylinder head but there has got to be a better solution.

Not one of the websites selling Big Bore kits for the TRX90 says anything about not being able to use the stock cylinder head. I'm sure someone out there has experienced this problem. The "tech guy" at the website I piurchased this from (as well as a few others I tried) were unaware of this issue which makes me question dealers that sell items that they have no experience installing or testing.

HELP!!!

Thanks,
Marc

[bnesbitt2]

I had the same problem and used jb weld and it worked fine,I eventually went with the racing head and a bigger carb and that made a huge difference.

[mrman5050]

Do you think the carb or head had the bigger overall impact on the performance gain? I have a bigger carb but wasn't looking to replace the head just yet.

Did you also go with the high volume oil pump? Have you experienced and loss of power due to overheating? This seems to be a common complaint with these mods.

My son does not race - this is strictly a trail machine. I was just looking to get some more bite out of a this dog.

[miniquaddad90]

Originally posted by bnesbitt2
I had the same problem and used jb weld and it worked fine,I eventually went with the racing head and a bigger carb and that made a huge difference.

Which head & carb are you using? I've been looking at the T.B. stuff and was curious on reliabilty.

[bnesbitt2]

we are running the t b stuff and a 22 mm mikini carb and have had no prolems at all. I just put together my other sons quad with the same stuff except a 26mm carb we are going to the track next weekend to run them side by side and see what setup is better. We had no overheating problem but they only race for 3 or 4 laps in our series.