Another 310cc build

I have 13000 MI on my wrr and about 4000 on the athen 290 kit, I now can hear the timing chain rattle a little, so next project I think I want the 3mm stroker kit, more torque will be nice

paulie1960 wrote:

Keep us up dated on where thumper lighten piston and try to weight piston assembly?

No work was done to the piston, all heavy metal was added to the crank to make it match the piston. Thumper Racing reported to me they were surprised how much weight they had to add to such a small crank assembly. This was most likely due to the 290 piston weighing somewhere in the vicinity of 20 grams heavier than the original. When I tear the engine apart I'll try to remember and pull out the kitchen scale to see what the actual differences are.

Still waiting to hear back from Lindsay Machine Racing, figured I have a minimum 3wks more of waiting before I can anticipate getting a call from them. Same goes for the suspension, I called to see if Travis of Go-Race Inc. had the opportunity to dig into the parts and I can only assume he's still on vacation or very busy. Either way, I'm playing the waiting game on parts.

In one of the previous posts I mentioned purchasing a set of custom side fairings that resemble the pieces found on the WRF models. Well, I purchased them and they're pretty good in terms of materials and acceptable in terms of fit. I'll get a better idea how they fit when I have the subframe back on the bike and everything lines up. As anticipated, I'm not impressed with the quality of the mounting brackets. IMHO, it won't take much to bend them into a wadded up mess and leave you frustrated. So I'll be making my own mounts that are welded to the subframe and use quarter turn fasteners like the ones I have on my roadrace zx6r. It'll be cleaner looking and much less "bolt on". My only concern is the snap-on lobster claw connection on the forward most portion of the fender is pop riveted onto the fairing. While I don't believe this is a high stress point when crashing, it does have me worried because it's made of a harder plastic than the fairing itself. Another issue is the conflict in fitment with my homemade Steg Pegs. I may have to remake the peg mounts to wrap around the fairing or just make a hole through it in the appropriate spot. This will most likely be another build thread when I add the secondary radiator.  I'll post pics of the fairing in the near future, 12hr shift has killed my motorvation, lol. Stay tuned!!!

paulie1960 wrote:

I have 13000 MI on my wrr and about 4000 on the athen 290 kit, I now can hear the timing chain rattle a little, so next project I think I want the 3mm stroker kit, more torque will be nice

Good to hear from someone who has owned the 290 kit for more than a few miles. That tells me the kit isn't as fragile as some would say. It's only in a few areas of my riding that I find the lack of torque to be an issue. Mostly in the open areas or snapping out of a corner where getting up to speed is desired. Also, when on the trails and I need to pop the front wheel up and the bike can't make it happen. I'm keeping my expectations modest and mostly focused on getting my bike operational. That way, any improvements will be seen as a positive. Although, I better see more than 27hp on the next dyno run, lol.

I'm BAAAAAAACK!!

Yes, it's been just over three months and I now have the cylinder and throttle body back in my posession. A bunch of things have taken place since my last post, but I didn't want to post filler material until I had the actual engine project back on track. Since my last posting I've received and installed the suspension, bought an aftermarket radiator, installed the Webike side fairings, and finally the cylinder head and throttle body.



Full service suspension rebuild with all the options Travis at Go Race has for this bike.



Myler Radiator



Webike side fairings temporarily installed.



Original valves were used for the trail friendly port and polish



Intake side (sorry for the fuzzy pics, very difficult to get the camera to focus)



Exhaust side



New throttle plate and +2mm overbore



Dark spot in the bore shows where epoxy has to be added when boring the opening. Yamaha was pretty skimpy with the casting dimensions!!



The other epoxy spot



Pic showing the match porting of the TB to cyl head. I believe the rubber coupler was opened up too although I haven't verified this.

I know a lot of you want to know what the flow numbers were for these parts, but that information was not given to me. It could be considered a competitive secret or just not given. Either way, the dyno will tell if the work paid off. As of this writing I've pulled the engine and have it almost completely apart. I'm at a stopping point due to needing a flywheel puller. I've also decided to take the precautionary route and purchase a bunch of items that will be difficult to replace one the engine is back together. I'll try to bring this post up to the current point in the build within the next week or two. Never realized how much writing goes into doing this stuff. I'm starting to wonder if I should make a YouTube channel and just talk my way through it, LOL. Until next time!

As previously stated, I’ve already started taking the engine apart. My first goal was to try and figure out why I lost all my compression. What I believe happened was oil starvation related. When I pulled the cylinder head I noticed a dark spot on the shim bucket on the exhaust side. This spot is where the hard chrome has chipped off and exposed the metal underneath. The cam lobe shows a dark streak which is most likely caused by the chip, but the chrome is still intact. Not really an issue as I purchased a 2nd head and cams for this project. If I was looking to just do the necessary repairs to put the bike back on the trail I would most likely be ok with just replacing the shim bucket (as far as I could tell).



The dark spot on the shim bucket is the hard chrome finish chipping off.



Looking at the cylinder bore I was expecting to see some evidence of the cylinder/rings failing and destroyingamage to the nikasil finish. To my surprise, there was no damage at all, the finish on the cylinder is still flawless and the only wear I can see is the piston moves VERY easily in the cylinder bore. In fact, the cross hatch pattern in the nikasil coating is still visible. So it’s most likely just heavily worn rings that brought this engine down.

Previously I mentioned taking the cautionary approach and decided to purchase a new timing chain, oil pump, retaining washer/clips, crankcase bearings and all the seals that either keep the fluids in the case or from mixing together. When I took a moment to realize how much work it was just to pull the engine it became a no brainer to make sure I didn’t have to do it again. While the budget for this build wasn’t a major consideration, I am getting to the point where I really have to justify a purchase as this is getting expensive, LOL.









After the crankcase was split I went over the transmission parts carefully just to make sure the shift forks and shift drum weren't compromised. I briefly had a shifting issue which was found to be the shifter hitting the lower mounting boss on the case that secures the OEM sprocket guard. Moving the shifter back down resolved the problem, but I wanted to make sure nothing was showing excess wear. The boss has been removed with an airsaw and carbide bit. The first reason for removal is so I can move the lever up a notch and try to find a better fit with my MX boots as I currently can’t up shift while standing up and not dipping my foot down excessively. The second reason is if the chain was to fail it could break the case by ripping out the mounting boss. The rest of the case is protected by a Sandman crankcase plate. A very simple and effective item.

All seals, bearings, and retaining clips have been ordered and should begin to arrive next week. I would be ok without replacing the bearings in the crankcase if I didn’t have plans to powdercoat the case, cylinder, and side covers. But in order to prep the case properly, sandblasting will be necessary to clean the metal surfaces and I’m not confident enough to say I could guarantee the bearings wouldn’t get compromised in the sand blasting or survive the removal process.

As I was coming to the end of this disassembly I realized I’m going to need a few more tools. I purchased a Motion Pro blind bearing puller kit, flywheel puller (a must have), crankshaft puller, and a valve removal tool for the reassembly. As it stands now I can’t remove 3 bearings due to not having access to the backside. I could pay a shop to do it for me, but shop hours here are about $90-ish/hour and I’d rather add to my tool inventory for future jobs. The crank puller is for pulling the crank into the bearings/crankcase during reassembly. I thought about using my 20 ton press, but fear I may damage the crank at the wrist pin. The tool is about $70 and in my opinion is worth the peace of mind.












A few weeks ago I stripped the finish off the sides of the frame and swingarm using a tool from Eastwood called the Surface Conditioning Tool (SCT) and coated them with their 2 part aerosol clearcoat. The finish you see is accomplished with a 180 grit wheel. I tried using the 320 grit finishing wheel and it started to take on a polished look which isn't what I wanted. I think the end result turned out pretty good and the finish hardness of the clearcoat is on par with that of a typical catalyzed clearcoat application. Using the SCT, the entire job took about 90 minutes to include painting the parts.

While I was taking the rear suspension apart to refinish the swingarm and frame I noticed the portion of the rear suspension linkage couldn't be moved by hand. In fact, it was almost completely seized in place. A complete rebuild kit cost approx. $71 dollars but I got lucky and found an entire OEM linkage assembly for $79 dollars shipped with only 350 miles on it. When inspecting the linkage, I noticed evidence of the lower shock mount grinding against the side. I'm sure this wouldn't have hurt anything, but for an extra $8 it seemed like a smart choice to replace it all.



So this brings me to were I'm at now. Once the items from Partzilla start arriving I'll be able to start the assembly process which hopefully will be much quicker. Until next time!!

i have 17000mi on my wrr and have about 8000mi on the athena kit, so this winter it will be over 20000mi so I may rebuild here with new athena piston and rings and maybe hotrods stroker crank, Did you have to address any compression increase with the stroker crank.

No, the compression was fine and no further adjustments were needed. I believe if memory serves me right it came out to 12.69:1. The engine is actually finished and running as of this writing. Unfortunately, my phone died and I need to figure out how to get my pictures of the build off of it so I can finish this thread.