Cbr Bore Up Kit Cam Chain Prob

[dimsum55]

Hi guys,

Sorry to drop in on your forum, just didn't know where else to post. I've noticed that a lot of you guys ride the CBR 150 and are well into your mods, so thought someone might be able to help me out... Cheers in advance.

Ok here's my problem, I've got a CBR 125 (I'm in the UK) and I ordered the 160 bore up kit from a reputable source in Thailand. The kit consisted of the barrel, piston and 2mm spacer. Seemed like a fairly easy swap, being from a family of mechanics. How wrong was I...

The main problem I encountered was that after including the spacer the barrel and head were thus 2mm higher which meant that my cam chain was too sort to fit on to the top end sprocket. My source told me that there should still be enough play in the chain to fit it on, if not then I was to sand down the spacer to 1.3mm or to stack paper gaskets. I tried stacking the gaskets which seemed to work until I turned the bike over and I heard the evil evil sound of the piston hitting the head. Next I resorted to using the sanded down spacer but the chain appeared to still be too short. So subsequently I took the piston and had it machined down by 1mm. This combined with the sanded down spacer and 2 extra thin gaskets for the spacer have just given me enough play to lever the sprocket and cam chain on to the head. I've got the bike running and I can def feel the power increase, although I haven't given it plenty in fear that the cam chain will snap. But this is my final worry as I can hear the chain whine incredibly loudly as there is no slack whatsoever. I've also had to increase the valve clearance because I was getting a very slight piston hit, so now although the piston doesn't hit, I think, the valves chatter.

So I was wondering if anyone had any ideas on how I can resolve this problem, of the cam chain mainly? I've made enquiries into buying a split chain and adding plus 2 links, but the guy at the shop told me that it probably wouldn't solve the problem as the chain would then be too long. I was wonderig if maybe the cbr 150 chain is slightly longer hence the bore up kit being able to fit easly with the 2mm spacer?

Anyway, my bike has been off the road for 2 weeks and I've built and dismantled the engine countless times, more than I care to remember. At the moment I'm thinking to cut my losses and get an original gasket set and revert back to stock as I have my full bike test in a weeks time and need to get some practice in. It's either that or keep riding with the bore up kit and gamble that the chain won't snap and destroy my engine completely.

Any help would be greatly appreciated, as this has been doing my head in! Thanks guys and hope all is well in the better part of the world!

Neil

[dave_boo]

I looked at www.aseanmoto.com and I didn't see a 160cc bore up for the CBR 125....are you sure they didn't send you the 160cc bore up for the CBR 150 (and I know it's a stupid question because the CBR 125 is a SOHC/2 valve, but we all overlook stuff)?

But even with that; I don't know why they would need a spacer (with the exception of preventing your pistons from beating the crap out of the valves because the piston was reliefed for 4 valves instead of 2 and therefore would start interfering). I'd recommend the obvious thing and check out the height difference between the two barrels; if there is none that it's definitely the piston that's to fault. Check the height of the piston over the pin for both; if you can get the piston machined down to the same height as the old without taking away too much material go for it.

The valve interference is of great concern; what you may be hearing is not valve chatter in the classical sense but rather the deformed lips of the valves striking the seat...not healthy in an engine that likes to be at 9000+ RPM.

Whatever it is I hope you the best of luck tracking down the problem and resolving it.

[dimsum55]

Hi, thanks for the info, appreciate it.

No I didn't order from asean moto, I went to akunar. I was communicating with the owner and for sure the kit is designed for the 125, in that the piston only has 2 valve cut outs on the surface. The barrel and the pisto nae the same height as the stock ones, the reason the spacer is needed, from what I can see, is because the squish area on the cylinder head is still only the standard bore so if I were not to use the spacer then the piston would hit the edge of the squish area as it is of a larger bore.

Thanks again for the info, you don't know if the cbr 150 chain is a bit longer?

[dave_boo]

Hi, thanks for the info, appreciate it.

No I didn't order from asean moto, I went to akunar. I was communicating with the owner and for sure the kit is designed for the 125, in that the piston only has 2 valve cut outs on the surface. The barrel and the pisto nae the same height as the stock ones, the reason the spacer is needed, from what I can see, is because the squish area on the cylinder head is still only the standard bore so if I were not to use the spacer then the piston would hit the edge of the squish area as it is of a larger bore.

Thanks again for the info, you don't know if the cbr 150 chain is a bit longer?

D'oh...forgot about the top of the combustion chamber. If you're happy with the machine shop you were using, get them to remove some material from the head; not sure how much play you have up there until you start seeing water passages however. You may be safe taking a mm off and it's cheaper than getting a new head that is the correct size. The other possibility is to remove yet more material from the piston...I wouldn't want to see that since you've already taken it down quite a bit. That would get you the 2mm that the spacer would have given you and the stock chain would be back to normal.

The CBR 150 is chain is going to be longer due to having to camshaft sprockets to go over; how much I can't tell you. But I'd assume that it would be quite a bit longer to the point that it's unusable in the 125.

[dimsum55]

Hi Dave_boo,

Thanks again for the info, I'm currently thinking of trying to get the squish area on the head rebored to the same diameter of the piston and then take the spacer down 0.3mm or something, hopefully this will give me a little more room to play with...

Yeah I'm not too sure about machining the piston any more, originally I asked the machining guy to take 2mm off but he was a bit hesitant saying that I risk having the piston explode, so he said he'd do 1mm.

Anyway after riding a bit more, I've noticed the cam chain whine has decreased a lot, I'm guessing the chain has stretched a little more... It's now just the valves and piston I'm a bit worried about... But I'll get it sorted!

Thanks again,

Neil

[squintypanda]

Hello dimsum, was wondering how the akunar borup kit is working for ya? I'm also considering ordering a kit for my CBR150 but haven't really seen much talk about them. Have you been satisfied with this kit? How is the reliability and what kind of horse power gains are we talking about? Did you order anythign else besides the kit? I.E. camshaft, etc. sorry for all the questions and thank you very much!

-Victor Lin