honda 450 crf

Kaikissa nelareissa on omat ongelmansa. Venttiilit ovat pirun kalliita ja niitä saa vaihdella aika taajaan. itse vaihdoin juuri omaan Yamahaan 3imuvenaa, 100€/kpl.

Jos Lontoo sujuu niin tässä on jotain juttua ko. hondasta:
2002-04 CRF450
The two most common problems with this model include intake valve wear on all model years and cam chain tensioners that go slack on the 2002 and 03 models. At first the intake valves wear was attributed to dirt bypassing the air filter, causing wear to the protective oxide coating on the titanium intake valves. Some of the other theories touted on the Internet included valve seats that are too hard, too soft of a valve spring, and too steep of a closing ramp on the camshaft. The most reliable solution for the intake valve problem is to install a Kibblewhite spring kit and Black Diamond stainless steel intake valves. The parts cost about $300. Ferrea also makes stainless steel valves and their product features lighter weight and are designed to work with RD brand single coil spring kits. Ron Hamp Cycle offers a choice of lightened Ferrea stainless valves or solid titanium valves with DLC (diamond-like coatings) in standard and oversized along with custom machine work.
There are two options for the cam chain tensioner. The least expensive choice is to buy a tensioner from a 2004 CRF450, which sells for about $52. The 2004 and later Honda part is greatly improved but it should be replaced every 100hrs. Factory Racing of Italy chose a different approach to the problem; they make a manual cam chain tensioner. However manual cam chain tensioners require frequent adjustment and a careful touch. Another area of concern on the Honda is a worn exhaust rocker arm roller. Look for a deep groove to appear in the center of the roller. That indicates that the bearing is worn. You can’t replace the roller itself because it isn’t available from Honda separately. You need to replace the entire rocker assembly, which sells for about $120. If you are a fervent Internet news group reader there are two things that are recommended that should never be attempted. They include grinding down the valve shim pads to give valve to tappet clearance, and installing Honda ATV steel intake valves with the stock springs. When a valve is worn so far that Honda doesn’t offer a small enough shim, its junk and needs to be replaced. With regards to changing valve materials, when you switch from a lightweight titanium valve to a heavier steel valve, you must also install a stiffer spring. One last thing that contradicts the Honda manual and Internet myths, never attempt to use valve grinding compound to pre-finish a titanium valve prior to installation. The gritty compound will damage the oxide coating designed to protect the valve.